mass renaming from offset/state to timezone/offset.

README.md

@@ -38,14 +38,14 @@ Chrono simply reexports it.
 Chrono provides a `DateTime` type for the combined date and time.
 
 `DateTime`, among others, is timezone-aware and
-must be constructed from the timezone object (`Offset`).
-`DateTime`s with different offsets do not mix, but can be converted to each other.
+must be constructed from the `TimeZone` object.
+`DateTime`s with different time zones do not mix, but can be converted to each other.
 
 You can get the current date and time in the UTC timezone (`UTC::now()`)
 or in the local timezone (`Local::now()`).
 
 ~~~~ {.rust}
-use chrono::{UTC, Local, DateTime};
+use chrono::*;
 
 let utc: DateTime<UTC> = UTC::now();       // e.g. `2014-11-28T12:45:59.324310806Z`
 let local: DateTime<Local> = Local::now(); // e.g. `2014-11-28T21:45:59.324310806+09:00`
@@ -56,7 +56,7 @@ This is a bit verbose due to Rust's lack of function and method overloading,
 but in turn we get a rich combination of initialization methods.
 
 ~~~~ {.rust}
-use chrono::{UTC, Offset, Weekday, LocalResult};
+use chrono::*;
 
 let dt = UTC.ymd(2014, 7, 8).and_hms(9, 10, 11); // `2014-07-08T09:10:11Z`
 // July 8 is 188th day of the year 2014 (`o` for "ordinal")
@@ -81,7 +81,7 @@ Addition and subtraction is also supported.
 The following illustrates most supported operations to the date and time:
 
 ~~~~ {.rust}
-use chrono::{UTC, Local, Datelike, Timelike, Weekday, Duration};
+use chrono::*;
 
 // assume this returned `2014-11-28T21:45:59.324310806+09:00`:
 let dt = Local::now();
@@ -95,9 +95,10 @@ assert_eq!(dt.weekday().number_from_monday(), 5); // Mon=1, ..., Sat=7
 assert_eq!(dt.ordinal(), 332); // the day of year
 assert_eq!(dt.num_days_from_ce(), 735565); // the number of days from and including Jan 1, 1
 
-// offset accessor and manipulation
+// time zone accessor and manipulation
 assert_eq!(dt.offset().local_minus_utc(), Duration::hours(9));
-assert_eq!(dt.with_offset(UTC), UTC.ymd(2014, 11, 28).and_hms_nano(12, 45, 59, 324310806));
+assert_eq!(dt.timezone(), FixedOffset::east(9 * 3600));
+assert_eq!(dt.with_timezone(&UTC), UTC.ymd(2014, 11, 28).and_hms_nano(12, 45, 59, 324310806));
 
 // a sample of property manipulations (validates dynamically)
 assert_eq!(dt.with_day(29).unwrap().weekday(), Weekday::Sat); // 2014-11-29 is Saturday
@@ -118,7 +119,7 @@ which format is equivalent to the familiar `strftime` format.
 The default `to_string` method and `{:?}` specifier also give a reasonable representation.
 
 ~~~~ {.rust}
-use chrono::{UTC, Offset};
+use chrono::*;
 
 let dt = UTC.ymd(2014, 11, 28).and_hms(12, 0, 9);
 assert_eq!(dt.format("%Y-%m-%d %H:%M:%S").to_string(), "2014-11-28 12:00:09");
@@ -132,12 +133,12 @@ assert_eq!(format!("{:?}", dt), "2014-11-28T12:00:09Z");
 ### Individual date and time
 
 Chrono also provides an individual date type (`Date`) and time type (`Time`).
-They also have offsets attached, and have to be constructed via offsets.
+They also have time zones attached, and have to be constructed via time zones.
 Most operations available to `DateTime` are also available to `Date` and `Time`
 whenever appropriate.
 
 ~~~~ {.rust}
-use chrono::{UTC, Local, Offset, LocalResult, Datelike, Weekday};
+use chrono::*;
 
 assert_eq!(UTC::today(), UTC::now().date());
 assert_eq!(Local::today(), Local::now().date());
@@ -156,7 +157,7 @@ Chrono provides naive counterparts to `Date`, `Time` and `DateTime`
 as `NaiveDate`, `NaiveTime` and `NaiveDateTime` respectively.
 
 They have almost equivalent interfaces as their timezone-aware twins,
-but are not associated to offsets obviously and can be quite low-level.
+but are not associated to time zones obviously and can be quite low-level.
 They are mostly useful for building blocks for higher-level types.
 
 ## Limitations
@@ -177,5 +178,5 @@ Any operation that can be ambiguous will return `None` in such cases.
 For example, "a month later" of 2014-01-30 is not well-defined
 and consequently `UTC.ymd(2014, 1, 30).with_month(2)` returns `None`.
 
-Advanced offset handling and date/time parsing is not yet supported (but is planned).
+Advanced time zone handling and date/time parsing is not yet supported (but is planned).
 

src/date.rs

@@ -12,7 +12,7 @@ use std::ops::{Add, Sub};
 
 use {Weekday, Datelike};
 use duration::Duration;
-use offset::{Offset, OffsetState};
+use offset::{TimeZone, Offset};
 use offset::utc::UTC;
 use naive;
 use naive::date::NaiveDate;
@@ -22,9 +22,9 @@ use format::DelayedFormat;
 
 /// ISO 8601 calendar date with time zone.
 #[derive(Clone)]
-pub struct Date<Off: Offset> {
+pub struct Date<Tz: TimeZone> {
     date: NaiveDate,
-    offset: Off::State,
+    offset: Tz::Offset,
 }
 
 /// The minimum possible `Date`.
@@ -32,13 +32,13 @@ pub const MIN: Date<UTC> = Date { date: naive::date::MIN, offset: UTC };
 /// The maximum possible `Date`.
 pub const MAX: Date<UTC> = Date { date: naive::date::MAX, offset: UTC };
 
-impl<Off: Offset> Date<Off> {
+impl<Tz: TimeZone> Date<Tz> {
     /// Makes a new `Date` with given *UTC* date and offset.
-    /// The local date should be constructed via the `Offset` trait.
+    /// The local date should be constructed via the `TimeZone` trait.
     //
     // note: this constructor is purposedly not named to `new` to discourage the direct usage.
     #[inline]
-    pub fn from_utc(date: NaiveDate, offset: Off::State) -> Date<Off> {
+    pub fn from_utc(date: NaiveDate, offset: Tz::Offset) -> Date<Tz> {
         Date { date: date, offset: offset }
     }
 
@@ -47,7 +47,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Fails on invalid datetime.
     #[inline]
-    pub fn and_time(&self, time: NaiveTime) -> Option<DateTime<Off>> {
+    pub fn and_time(&self, time: NaiveTime) -> Option<DateTime<Tz>> {
         let localdt = self.naive_local().and_time(time);
         self.timezone().from_local_datetime(&localdt).single()
     }
@@ -57,7 +57,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Fails on invalid hour, minute and/or second.
     #[inline]
-    pub fn and_hms(&self, hour: u32, min: u32, sec: u32) -> DateTime<Off> {
+    pub fn and_hms(&self, hour: u32, min: u32, sec: u32) -> DateTime<Tz> {
         self.and_hms_opt(hour, min, sec).expect("invalid time")
     }
 
@@ -66,7 +66,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Returns `None` on invalid hour, minute and/or second.
     #[inline]
-    pub fn and_hms_opt(&self, hour: u32, min: u32, sec: u32) -> Option<DateTime<Off>> {
+    pub fn and_hms_opt(&self, hour: u32, min: u32, sec: u32) -> Option<DateTime<Tz>> {
         NaiveTime::from_hms_opt(hour, min, sec).and_then(|time| self.and_time(time))
     }
 
@@ -76,7 +76,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Fails on invalid hour, minute, second and/or millisecond.
     #[inline]
-    pub fn and_hms_milli(&self, hour: u32, min: u32, sec: u32, milli: u32) -> DateTime<Off> {
+    pub fn and_hms_milli(&self, hour: u32, min: u32, sec: u32, milli: u32) -> DateTime<Tz> {
         self.and_hms_milli_opt(hour, min, sec, milli).expect("invalid time")
     }
 
@@ -87,7 +87,7 @@ impl<Off: Offset> Date<Off> {
     /// Returns `None` on invalid hour, minute, second and/or millisecond.
     #[inline]
     pub fn and_hms_milli_opt(&self, hour: u32, min: u32, sec: u32,
-                             milli: u32) -> Option<DateTime<Off>> {
+                             milli: u32) -> Option<DateTime<Tz>> {
         NaiveTime::from_hms_milli_opt(hour, min, sec, milli).and_then(|time| self.and_time(time))
     }
 
@@ -97,7 +97,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Fails on invalid hour, minute, second and/or microsecond.
     #[inline]
-    pub fn and_hms_micro(&self, hour: u32, min: u32, sec: u32, micro: u32) -> DateTime<Off> {
+    pub fn and_hms_micro(&self, hour: u32, min: u32, sec: u32, micro: u32) -> DateTime<Tz> {
         self.and_hms_micro_opt(hour, min, sec, micro).expect("invalid time")
     }
 
@@ -108,7 +108,7 @@ impl<Off: Offset> Date<Off> {
     /// Returns `None` on invalid hour, minute, second and/or microsecond.
     #[inline]
     pub fn and_hms_micro_opt(&self, hour: u32, min: u32, sec: u32,
-                             micro: u32) -> Option<DateTime<Off>> {
+                             micro: u32) -> Option<DateTime<Tz>> {
         NaiveTime::from_hms_micro_opt(hour, min, sec, micro).and_then(|time| self.and_time(time))
     }
 
@@ -118,7 +118,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Fails on invalid hour, minute, second and/or nanosecond.
     #[inline]
-    pub fn and_hms_nano(&self, hour: u32, min: u32, sec: u32, nano: u32) -> DateTime<Off> {
+    pub fn and_hms_nano(&self, hour: u32, min: u32, sec: u32, nano: u32) -> DateTime<Tz> {
         self.and_hms_nano_opt(hour, min, sec, nano).expect("invalid time")
     }
 
@@ -129,7 +129,7 @@ impl<Off: Offset> Date<Off> {
     /// Returns `None` on invalid hour, minute, second and/or nanosecond.
     #[inline]
     pub fn and_hms_nano_opt(&self, hour: u32, min: u32, sec: u32,
-                            nano: u32) -> Option<DateTime<Off>> {
+                            nano: u32) -> Option<DateTime<Tz>> {
         NaiveTime::from_hms_nano_opt(hour, min, sec, nano).and_then(|time| self.and_time(time))
     }
 
@@ -137,7 +137,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Fails when `self` is the last representable date.
     #[inline]
-    pub fn succ(&self) -> Date<Off> {
+    pub fn succ(&self) -> Date<Tz> {
         self.succ_opt().expect("out of bound")
     }
 
@@ -145,7 +145,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Returns `None` when `self` is the last representable date.
     #[inline]
-    pub fn succ_opt(&self) -> Option<Date<Off>> {
+    pub fn succ_opt(&self) -> Option<Date<Tz>> {
         self.date.succ_opt().map(|date| Date::from_utc(date, self.offset.clone()))
     }
 
@@ -153,7 +153,7 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Fails when `self` is the first representable date.
     #[inline]
-    pub fn pred(&self) -> Date<Off> {
+    pub fn pred(&self) -> Date<Tz> {
         self.pred_opt().expect("out of bound")
     }
 
@@ -161,26 +161,26 @@ impl<Off: Offset> Date<Off> {
     ///
     /// Returns `None` when `self` is the first representable date.
     #[inline]
-    pub fn pred_opt(&self) -> Option<Date<Off>> {
+    pub fn pred_opt(&self) -> Option<Date<Tz>> {
         self.date.pred_opt().map(|date| Date::from_utc(date, self.offset.clone()))
     }
 
-    /// Retrieves an associated offset state.
+    /// Retrieves an associated offset from UTC.
     #[inline]
-    pub fn offset<'a>(&'a self) -> &'a Off::State {
+    pub fn offset<'a>(&'a self) -> &'a Tz::Offset {
         &self.offset
     }
 
-    /// Retrieves an associated offset.
+    /// Retrieves an associated time zone.
     #[inline]
-    pub fn timezone(&self) -> Off {
-        Offset::from_state(&self.offset)
+    pub fn timezone(&self) -> Tz {
+        TimeZone::from_offset(&self.offset)
     }
 
-    /// Changes the associated offset.
+    /// Changes the associated time zone.
     /// This does not change the actual `Date` (but will change the string representation).
     #[inline]
-    pub fn with_timezone<Off2: Offset>(&self, tz: &Off2) -> Date<Off2> {
+    pub fn with_timezone<Tz2: TimeZone>(&self, tz: &Tz2) -> Date<Tz2> {
         tz.from_utc_date(&self.date)
     }
 
@@ -198,12 +198,12 @@ impl<Off: Offset> Date<Off> {
 }
 
 /// Maps the local date to other date with given conversion function.
-fn map_local<Off: Offset, F>(d: &Date<Off>, mut f: F) -> Option<Date<Off>>
+fn map_local<Tz: TimeZone, F>(d: &Date<Tz>, mut f: F) -> Option<Date<Tz>>
         where F: FnMut(NaiveDate) -> Option<NaiveDate> {
     f(d.naive_local()).and_then(|date| d.timezone().from_local_date(&date).single())
 }
 
-impl<Off: Offset> Date<Off> where Off::State: fmt::Display {
+impl<Tz: TimeZone> Date<Tz> where Tz::Offset: fmt::Display {
     /// Formats the date in the specified format string.
     /// See the `format` module on the supported escape sequences.
     #[inline]
@@ -212,7 +212,7 @@ impl<Off: Offset> Date<Off> where Off::State: fmt::Display {
     }
 }
 
-impl<Off: Offset> Datelike for Date<Off> {
+impl<Tz: TimeZone> Datelike for Date<Tz> {
     #[inline] fn year(&self) -> i32 { self.naive_local().year() }
     #[inline] fn month(&self) -> u32 { self.naive_local().month() }
     #[inline] fn month0(&self) -> u32 { self.naive_local().month0() }
@@ -224,90 +224,90 @@ impl<Off: Offset> Datelike for Date<Off> {
     #[inline] fn isoweekdate(&self) -> (i32, u32, Weekday) { self.naive_local().isoweekdate() }
 
     #[inline]
-    fn with_year(&self, year: i32) -> Option<Date<Off>> {
+    fn with_year(&self, year: i32) -> Option<Date<Tz>> {
         map_local(self, |date| date.with_year(year))
     }
 
     #[inline]
-    fn with_month(&self, month: u32) -> Option<Date<Off>> {
+    fn with_month(&self, month: u32) -> Option<Date<Tz>> {
         map_local(self, |date| date.with_month(month))
     }
 
     #[inline]
-    fn with_month0(&self, month0: u32) -> Option<Date<Off>> {
+    fn with_month0(&self, month0: u32) -> Option<Date<Tz>> {
         map_local(self, |date| date.with_month0(month0))
     }
 
     #[inline]
-    fn with_day(&self, day: u32) -> Option<Date<Off>> {
+    fn with_day(&self, day: u32) -> Option<Date<Tz>> {
         map_local(self, |date| date.with_day(day))
     }
 
     #[inline]
-    fn with_day0(&self, day0: u32) -> Option<Date<Off>> {
+    fn with_day0(&self, day0: u32) -> Option<Date<Tz>> {
         map_local(self, |date| date.with_day0(day0))
     }
 
     #[inline]
-    fn with_ordinal(&self, ordinal: u32) -> Option<Date<Off>> {
+    fn with_ordinal(&self, ordinal: u32) -> Option<Date<Tz>> {
         map_local(self, |date| date.with_ordinal(ordinal))
     }
 
     #[inline]
-    fn with_ordinal0(&self, ordinal0: u32) -> Option<Date<Off>> {
+    fn with_ordinal0(&self, ordinal0: u32) -> Option<Date<Tz>> {
         map_local(self, |date| date.with_ordinal0(ordinal0))
     }
 }
 
-impl<Off: Offset, Off2: Offset> PartialEq<Date<Off2>> for Date<Off> {
-    fn eq(&self, other: &Date<Off2>) -> bool { self.date == other.date }
+impl<Tz: TimeZone, Tz2: TimeZone> PartialEq<Date<Tz2>> for Date<Tz> {
+    fn eq(&self, other: &Date<Tz2>) -> bool { self.date == other.date }
 }
 
-impl<Off: Offset> Eq for Date<Off> {
+impl<Tz: TimeZone> Eq for Date<Tz> {
 }
 
-impl<Off: Offset> PartialOrd for Date<Off> {
-    fn partial_cmp(&self, other: &Date<Off>) -> Option<Ordering> {
+impl<Tz: TimeZone> PartialOrd for Date<Tz> {
+    fn partial_cmp(&self, other: &Date<Tz>) -> Option<Ordering> {
         self.date.partial_cmp(&other.date)
     }
 }
 
-impl<Off: Offset> Ord for Date<Off> {
-    fn cmp(&self, other: &Date<Off>) -> Ordering { self.date.cmp(&other.date) }
+impl<Tz: TimeZone> Ord for Date<Tz> {
+    fn cmp(&self, other: &Date<Tz>) -> Ordering { self.date.cmp(&other.date) }
 }
 
-impl<Off: Offset, H: hash::Hasher + hash::Writer> hash::Hash<H> for Date<Off> {
+impl<Tz: TimeZone, H: hash::Hasher + hash::Writer> hash::Hash<H> for Date<Tz> {
     fn hash(&self, state: &mut H) { self.date.hash(state) }
 }
 
-impl<Off: Offset> Add<Duration> for Date<Off> {
-    type Output = Date<Off>;
+impl<Tz: TimeZone> Add<Duration> for Date<Tz> {
+    type Output = Date<Tz>;
 
-    fn add(self, rhs: Duration) -> Date<Off> {
+    fn add(self, rhs: Duration) -> Date<Tz> {
         Date { date: self.date + rhs, offset: self.offset }
     }
 }
 
-impl<Off: Offset, Off2: Offset> Sub<Date<Off2>> for Date<Off> {
+impl<Tz: TimeZone, Tz2: TimeZone> Sub<Date<Tz2>> for Date<Tz> {
     type Output = Duration;
 
-    fn sub(self, rhs: Date<Off2>) -> Duration { self.date - rhs.date }
+    fn sub(self, rhs: Date<Tz2>) -> Duration { self.date - rhs.date }
 }
 
-impl<Off: Offset> Sub<Duration> for Date<Off> {
-    type Output = Date<Off>;
+impl<Tz: TimeZone> Sub<Duration> for Date<Tz> {
+    type Output = Date<Tz>;
 
     #[inline]
-    fn sub(self, rhs: Duration) -> Date<Off> { self.add(-rhs) }
+    fn sub(self, rhs: Duration) -> Date<Tz> { self.add(-rhs) }
 }
 
-impl<Off: Offset> fmt::Debug for Date<Off> {
+impl<Tz: TimeZone> fmt::Debug for Date<Tz> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:?}{:?}", self.naive_local(), self.offset)
     }
 }
 
-impl<Off: Offset> fmt::Display for Date<Off> where Off::State: fmt::Display {
+impl<Tz: TimeZone> fmt::Display for Date<Tz> where Tz::Offset: fmt::Display {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}{}", self.naive_local(), self.offset)
     }
@@ -321,7 +321,7 @@ mod tests {
     use naive::date::NaiveDate;
     use naive::time::NaiveTime;
     use naive::datetime::NaiveDateTime;
-    use offset::{Offset, OffsetState, LocalResult};
+    use offset::{TimeZone, Offset, LocalResult};
 
     #[derive(Copy, Clone, PartialEq, Eq)]
     struct UTC1y; // same to UTC but with an offset of 365 days
@@ -329,27 +329,27 @@ mod tests {
     #[derive(Copy, Clone, PartialEq, Eq)]
     struct OneYear;
 
-    impl Offset for UTC1y {
-        type State = OneYear;
+    impl TimeZone for UTC1y {
+        type Offset = OneYear;
 
-        fn from_state(_state: &OneYear) -> UTC1y { UTC1y }
+        fn from_offset(_offset: &OneYear) -> UTC1y { UTC1y }
 
-        fn state_from_local_date(&self, _local: &NaiveDate) -> LocalResult<OneYear> {
+        fn offset_from_local_date(&self, _local: &NaiveDate) -> LocalResult<OneYear> {
             LocalResult::Single(OneYear)
         }
-        fn state_from_local_time(&self, _local: &NaiveTime) -> LocalResult<OneYear> {
+        fn offset_from_local_time(&self, _local: &NaiveTime) -> LocalResult<OneYear> {
             LocalResult::Single(OneYear)
         }
-        fn state_from_local_datetime(&self, _local: &NaiveDateTime) -> LocalResult<OneYear> {
+        fn offset_from_local_datetime(&self, _local: &NaiveDateTime) -> LocalResult<OneYear> {
             LocalResult::Single(OneYear)
         }
 
-        fn state_from_utc_date(&self, _utc: &NaiveDate) -> OneYear { OneYear }
-        fn state_from_utc_time(&self, _utc: &NaiveTime) -> OneYear { OneYear }
-        fn state_from_utc_datetime(&self, _utc: &NaiveDateTime) -> OneYear { OneYear }
+        fn offset_from_utc_date(&self, _utc: &NaiveDate) -> OneYear { OneYear }
+        fn offset_from_utc_time(&self, _utc: &NaiveTime) -> OneYear { OneYear }
+        fn offset_from_utc_datetime(&self, _utc: &NaiveDateTime) -> OneYear { OneYear }
     }
 
-    impl OffsetState for OneYear {
+    impl Offset for OneYear {
         fn local_minus_utc(&self) -> Duration { Duration::days(365) }
     }
 

src/datetime.rs

@@ -3,7 +3,7 @@
 // See README.md and LICENSE.txt for details.
 
 /*!
- * ISO 8601 date and time.
+ * ISO 8601 date and time with time zone.
  */
 
 use std::{fmt, hash};
@@ -11,7 +11,7 @@ use std::cmp::Ordering;
 use std::ops::{Add, Sub};
 
 use {Weekday, Timelike, Datelike};
-use offset::{Offset, OffsetState};
+use offset::{TimeZone, Offset};
 use duration::Duration;
 use naive::datetime::NaiveDateTime;
 use time::Time;
@@ -20,30 +20,30 @@ use format::DelayedFormat;
 
 /// ISO 8601 combined date and time with time zone.
 #[derive(Clone)]
-pub struct DateTime<Off: Offset> {
+pub struct DateTime<Tz: TimeZone> {
     datetime: NaiveDateTime,
-    offset: Off::State,
+    offset: Tz::Offset,
 }
 
-impl<Off: Offset> DateTime<Off> {
+impl<Tz: TimeZone> DateTime<Tz> {
     /// Makes a new `DateTime` with given *UTC* datetime and offset.
-    /// The local datetime should be constructed via the `Offset` trait.
+    /// The local datetime should be constructed via the `TimeZone` trait.
     //
     // note: this constructor is purposedly not named to `new` to discourage the direct usage.
     #[inline]
-    pub fn from_utc(datetime: NaiveDateTime, offset: Off::State) -> DateTime<Off> {
+    pub fn from_utc(datetime: NaiveDateTime, offset: Tz::Offset) -> DateTime<Tz> {
         DateTime { datetime: datetime, offset: offset }
     }
 
     /// Retrieves a date component.
     #[inline]
-    pub fn date(&self) -> Date<Off> {
+    pub fn date(&self) -> Date<Tz> {
         Date::from_utc(self.datetime.date().clone(), self.offset.clone())
     }
 
     /// Retrieves a time component.
     #[inline]
-    pub fn time(&self) -> Time<Off> {
+    pub fn time(&self) -> Time<Tz> {
         Time::from_utc(self.datetime.time().clone(), self.offset.clone())
     }
 
@@ -53,22 +53,22 @@ impl<Off: Offset> DateTime<Off> {
         self.datetime.num_seconds_from_unix_epoch()
     }
 
-    /// Retrieves an associated offset state.
+    /// Retrieves an associated offset from UTC.
     #[inline]
-    pub fn offset<'a>(&'a self) -> &'a Off::State {
+    pub fn offset<'a>(&'a self) -> &'a Tz::Offset {
         &self.offset
     }
 
-    /// Retrieves an associated offset.
+    /// Retrieves an associated time zone.
     #[inline]
-    pub fn timezone(&self) -> Off {
-        Offset::from_state(&self.offset)
+    pub fn timezone(&self) -> Tz {
+        TimeZone::from_offset(&self.offset)
     }
 
-    /// Changes the associated offset.
+    /// Changes the associated time zone.
     /// This does not change the actual `DateTime` (but will change the string representation).
     #[inline]
-    pub fn with_timezone<Off2: Offset>(&self, tz: &Off2) -> DateTime<Off2> {
+    pub fn with_timezone<Tz2: TimeZone>(&self, tz: &Tz2) -> DateTime<Tz2> {
         tz.from_utc_datetime(&self.datetime)
     }
 
@@ -86,12 +86,12 @@ impl<Off: Offset> DateTime<Off> {
 }
 
 /// Maps the local datetime to other datetime with given conversion function.
-fn map_local<Off: Offset, F>(dt: &DateTime<Off>, mut f: F) -> Option<DateTime<Off>>
+fn map_local<Tz: TimeZone, F>(dt: &DateTime<Tz>, mut f: F) -> Option<DateTime<Tz>>
         where F: FnMut(NaiveDateTime) -> Option<NaiveDateTime> {
     f(dt.naive_local()).and_then(|datetime| dt.timezone().from_local_datetime(&datetime).single())
 }
 
-impl<Off: Offset> DateTime<Off> where Off::State: fmt::Display {
+impl<Tz: TimeZone> DateTime<Tz> where Tz::Offset: fmt::Display {
     /// Formats the combined date and time in the specified format string.
     /// See the `format` module on the supported escape sequences.
     #[inline]
@@ -101,7 +101,7 @@ impl<Off: Offset> DateTime<Off> where Off::State: fmt::Display {
     }
 }
 
-impl<Off: Offset> Datelike for DateTime<Off> {
+impl<Tz: TimeZone> Datelike for DateTime<Tz> {
     #[inline] fn year(&self) -> i32 { self.naive_local().year() }
     #[inline] fn month(&self) -> u32 { self.naive_local().month() }
     #[inline] fn month0(&self) -> u32 { self.naive_local().month0() }
@@ -113,117 +113,117 @@ impl<Off: Offset> Datelike for DateTime<Off> {
     #[inline] fn isoweekdate(&self) -> (i32, u32, Weekday) { self.naive_local().isoweekdate() }
 
     #[inline]
-    fn with_year(&self, year: i32) -> Option<DateTime<Off>> {
+    fn with_year(&self, year: i32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_year(year))
     }
 
     #[inline]
-    fn with_month(&self, month: u32) -> Option<DateTime<Off>> {
+    fn with_month(&self, month: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_month(month))
     }
 
     #[inline]
-    fn with_month0(&self, month0: u32) -> Option<DateTime<Off>> {
+    fn with_month0(&self, month0: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_month0(month0))
     }
 
     #[inline]
-    fn with_day(&self, day: u32) -> Option<DateTime<Off>> {
+    fn with_day(&self, day: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_day(day))
     }
 
     #[inline]
-    fn with_day0(&self, day0: u32) -> Option<DateTime<Off>> {
+    fn with_day0(&self, day0: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_day0(day0))
     }
 
     #[inline]
-    fn with_ordinal(&self, ordinal: u32) -> Option<DateTime<Off>> {
+    fn with_ordinal(&self, ordinal: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_ordinal(ordinal))
     }
 
     #[inline]
-    fn with_ordinal0(&self, ordinal0: u32) -> Option<DateTime<Off>> {
+    fn with_ordinal0(&self, ordinal0: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_ordinal0(ordinal0))
     }
 }
 
-impl<Off: Offset> Timelike for DateTime<Off> {
+impl<Tz: TimeZone> Timelike for DateTime<Tz> {
     #[inline] fn hour(&self) -> u32 { self.naive_local().hour() }
     #[inline] fn minute(&self) -> u32 { self.naive_local().minute() }
     #[inline] fn second(&self) -> u32 { self.naive_local().second() }
     #[inline] fn nanosecond(&self) -> u32 { self.naive_local().nanosecond() }
 
     #[inline]
-    fn with_hour(&self, hour: u32) -> Option<DateTime<Off>> {
+    fn with_hour(&self, hour: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_hour(hour))
     }
 
     #[inline]
-    fn with_minute(&self, min: u32) -> Option<DateTime<Off>> {
+    fn with_minute(&self, min: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_minute(min))
     }
 
     #[inline]
-    fn with_second(&self, sec: u32) -> Option<DateTime<Off>> {
+    fn with_second(&self, sec: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_second(sec))
     }
 
     #[inline]
-    fn with_nanosecond(&self, nano: u32) -> Option<DateTime<Off>> {
+    fn with_nanosecond(&self, nano: u32) -> Option<DateTime<Tz>> {
         map_local(self, |datetime| datetime.with_nanosecond(nano))
     }
 }
 
-impl<Off: Offset, Off2: Offset> PartialEq<DateTime<Off2>> for DateTime<Off> {
-    fn eq(&self, other: &DateTime<Off2>) -> bool { self.datetime == other.datetime }
+impl<Tz: TimeZone, Tz2: TimeZone> PartialEq<DateTime<Tz2>> for DateTime<Tz> {
+    fn eq(&self, other: &DateTime<Tz2>) -> bool { self.datetime == other.datetime }
 }
 
-impl<Off: Offset> Eq for DateTime<Off> {
+impl<Tz: TimeZone> Eq for DateTime<Tz> {
 }
 
-impl<Off: Offset> PartialOrd for DateTime<Off> {
-    fn partial_cmp(&self, other: &DateTime<Off>) -> Option<Ordering> {
+impl<Tz: TimeZone> PartialOrd for DateTime<Tz> {
+    fn partial_cmp(&self, other: &DateTime<Tz>) -> Option<Ordering> {
         self.datetime.partial_cmp(&other.datetime)
     }
 }
 
-impl<Off: Offset> Ord for DateTime<Off> {
-    fn cmp(&self, other: &DateTime<Off>) -> Ordering { self.datetime.cmp(&other.datetime) }
+impl<Tz: TimeZone> Ord for DateTime<Tz> {
+    fn cmp(&self, other: &DateTime<Tz>) -> Ordering { self.datetime.cmp(&other.datetime) }
 }
 
-impl<Off: Offset, H: hash::Hasher + hash::Writer> hash::Hash<H> for DateTime<Off> {
+impl<Tz: TimeZone, H: hash::Hasher + hash::Writer> hash::Hash<H> for DateTime<Tz> {
     fn hash(&self, state: &mut H) { self.datetime.hash(state) }
 }
 
-impl<Off: Offset> Add<Duration> for DateTime<Off> {
-    type Output = DateTime<Off>;
+impl<Tz: TimeZone> Add<Duration> for DateTime<Tz> {
+    type Output = DateTime<Tz>;
 
-    fn add(self, rhs: Duration) -> DateTime<Off> {
+    fn add(self, rhs: Duration) -> DateTime<Tz> {
         DateTime { datetime: self.datetime + rhs, offset: self.offset }
     }
 }
 
-impl<Off: Offset, Off2: Offset> Sub<DateTime<Off2>> for DateTime<Off> {
+impl<Tz: TimeZone, Tz2: TimeZone> Sub<DateTime<Tz2>> for DateTime<Tz> {
     type Output = Duration;
 
-    fn sub(self, rhs: DateTime<Off2>) -> Duration { self.datetime - rhs.datetime }
+    fn sub(self, rhs: DateTime<Tz2>) -> Duration { self.datetime - rhs.datetime }
 }
 
-impl<Off: Offset> Sub<Duration> for DateTime<Off> {
-    type Output = DateTime<Off>;
+impl<Tz: TimeZone> Sub<Duration> for DateTime<Tz> {
+    type Output = DateTime<Tz>;
 
     #[inline]
-    fn sub(self, rhs: Duration) -> DateTime<Off> { self.add(-rhs) }
+    fn sub(self, rhs: Duration) -> DateTime<Tz> { self.add(-rhs) }
 }
 
-impl<Off: Offset> fmt::Debug for DateTime<Off> {
+impl<Tz: TimeZone> fmt::Debug for DateTime<Tz> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:?}{:?}", self.naive_local(), self.offset)
     }
 }
 
-impl<Off: Offset> fmt::Display for DateTime<Off> where Off::State: fmt::Display {
+impl<Tz: TimeZone> fmt::Display for DateTime<Tz> where Tz::Offset: fmt::Display {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{} {}", self.naive_local(), self.offset)
     }
@@ -233,7 +233,7 @@ impl<Off: Offset> fmt::Display for DateTime<Off> where Off::State: fmt::Display
 mod tests {
     use {Datelike};
     use duration::Duration;
-    use offset::Offset;
+    use offset::TimeZone;
     use offset::utc::UTC;
     use offset::local::Local;
     use offset::fixed::FixedOffset;

src/format.rs

@@ -10,7 +10,7 @@ use std::fmt;
 
 use {Datelike, Timelike};
 use duration::Duration;
-use offset::OffsetState;
+use offset::Offset;
 use naive::date::NaiveDate;
 use naive::time::NaiveTime;
 
@@ -198,11 +198,11 @@ impl<'a> DelayedFormat<'a> {
         DelayedFormat { date: date, time: time, off: None, fmt: fmt }
     }
 
-    /// Makes a new `DelayedFormat` value out of local date and time with offset state.
+    /// Makes a new `DelayedFormat` value out of local date and time with offset.
     pub fn new_with_offset<Off>(date: Option<NaiveDate>, time: Option<NaiveTime>,
-                                state: &Off, fmt: &'a str) -> DelayedFormat<'a>
-            where Off: OffsetState + fmt::Display {
-        let name_and_diff = (state.to_string(), state.local_minus_utc());
+                                offset: &Off, fmt: &'a str) -> DelayedFormat<'a>
+            where Off: Offset + fmt::Display {
+        let name_and_diff = (offset.to_string(), offset.local_minus_utc());
         DelayedFormat { date: date, time: time, off: Some(name_and_diff), fmt: fmt }
     }
 }

src/lib.rs

@@ -34,8 +34,8 @@ Chrono simply reexports it.
 Chrono provides a `DateTime` type for the combined date and time.
 
 `DateTime`, among others, is timezone-aware and
-must be constructed from the timezone object (`Offset`).
-`DateTime`s with different offsets do not mix, but can be converted to each other.
+must be constructed from the `TimeZone` object.
+`DateTime`s with different time zones do not mix, but can be converted to each other.
 
 You can get the current date and time in the UTC timezone (`UTC::now()`)
 or in the local timezone (`Local::now()`).
@@ -95,8 +95,9 @@ assert_eq!(dt.weekday().number_from_monday(), 5); // Mon=1, ..., Sat=7
 assert_eq!(dt.ordinal(), 332); // the day of year
 assert_eq!(dt.num_days_from_ce(), 735565); // the number of days from and including Jan 1, 1
 
-// offset accessor and manipulation
+// time zone accessor and manipulation
 assert_eq!(dt.offset().local_minus_utc(), Duration::hours(9));
+assert_eq!(dt.timezone(), FixedOffset::east(9 * 3600));
 assert_eq!(dt.with_timezone(&UTC), UTC.ymd(2014, 11, 28).and_hms_nano(12, 45, 59, 324310806));
 
 // a sample of property manipulations (validates dynamically)
@@ -132,7 +133,7 @@ assert_eq!(format!("{:?}", dt), "2014-11-28T12:00:09Z");
 ### Individual date and time
 
 Chrono also provides an individual date type (`Date`) and time type (`Time`).
-They also have offsets attached, and have to be constructed via offsets.
+They also have time zones attached, and have to be constructed via time zones.
 Most operations available to `DateTime` are also available to `Date` and `Time`
 whenever appropriate.
 
@@ -157,7 +158,7 @@ Chrono provides naive counterparts to `Date`, `Time` and `DateTime`
 as `NaiveDate`, `NaiveTime` and `NaiveDateTime` respectively.
 
 They have almost equivalent interfaces as their timezone-aware twins,
-but are not associated to offsets obviously and can be quite low-level.
+but are not associated to time zones obviously and can be quite low-level.
 They are mostly useful for building blocks for higher-level types.
 
 ## Limitations
@@ -178,7 +179,7 @@ Any operation that can be ambiguous will return `None` in such cases.
 For example, "a month later" of 2014-01-30 is not well-defined
 and consequently `UTC.ymd(2014, 1, 30).with_month(2)` returns `None`.
 
-Advanced offset handling and date/time parsing is not yet supported (but is planned).
+Advanced time zone handling and date/time parsing is not yet supported (but is planned).
 
 */
 
@@ -191,7 +192,7 @@ Advanced offset handling and date/time parsing is not yet supported (but is plan
 extern crate "time" as stdtime;
 
 pub use duration::Duration;
-pub use offset::{Offset, OffsetState, LocalResult};
+pub use offset::{TimeZone, Offset, LocalResult};
 pub use offset::utc::UTC;
 pub use offset::fixed::FixedOffset;
 pub use offset::local::Local;
@@ -214,7 +215,7 @@ pub mod offset;
 pub mod naive {
     //! Date and time types which do not concern about the timezones.
     //!
-    //! They are primarily building blocks for other types (e.g. `Offset`),
+    //! They are primarily building blocks for other types (e.g. `TimeZone`),
     //! but can be also used for the simpler date and time handling.
     pub mod date;
     pub mod time;

src/naive/time.rs

@@ -12,7 +12,6 @@ use std::ops::{Add, Sub};
 
 use Timelike;
 use div::div_mod_floor;
-use offset::Offset;
 use duration::Duration;
 use format::DelayedFormat;
 

src/offset/fixed.rs

@@ -13,9 +13,9 @@ use duration::Duration;
 use naive::date::NaiveDate;
 use naive::time::NaiveTime;
 use naive::datetime::NaiveDateTime;
-use super::{Offset, OffsetState, LocalResult};
+use super::{TimeZone, Offset, LocalResult};
 
-/// The fixed offset (and also state), from UTC-23:59:59 to UTC+23:59:59.
+/// The time zone with fixed offset, from UTC-23:59:59 to UTC+23:59:59.
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub struct FixedOffset {
     local_minus_utc: i32,
@@ -63,27 +63,27 @@ impl FixedOffset {
     }
 }
 
+impl TimeZone for FixedOffset {
+    type Offset = FixedOffset;
+
+    fn from_offset(offset: &FixedOffset) -> FixedOffset { offset.clone() }
+
+    fn offset_from_local_date(&self, _local: &NaiveDate) -> LocalResult<FixedOffset> {
+        LocalResult::Single(self.clone())
+    }
+    fn offset_from_local_time(&self, _local: &NaiveTime) -> LocalResult<FixedOffset> {
+        LocalResult::Single(self.clone())
+    }
+    fn offset_from_local_datetime(&self, _local: &NaiveDateTime) -> LocalResult<FixedOffset> {
+        LocalResult::Single(self.clone())
+    }
+
+    fn offset_from_utc_date(&self, _utc: &NaiveDate) -> FixedOffset { self.clone() }
+    fn offset_from_utc_time(&self, _utc: &NaiveTime) -> FixedOffset { self.clone() }
+    fn offset_from_utc_datetime(&self, _utc: &NaiveDateTime) -> FixedOffset { self.clone() }
+}
+
 impl Offset for FixedOffset {
-    type State = FixedOffset;
-
-    fn from_state(state: &FixedOffset) -> FixedOffset { state.clone() }
-
-    fn state_from_local_date(&self, _local: &NaiveDate) -> LocalResult<FixedOffset> {
-        LocalResult::Single(self.clone())
-    }
-    fn state_from_local_time(&self, _local: &NaiveTime) -> LocalResult<FixedOffset> {
-        LocalResult::Single(self.clone())
-    }
-    fn state_from_local_datetime(&self, _local: &NaiveDateTime) -> LocalResult<FixedOffset> {
-        LocalResult::Single(self.clone())
-    }
-
-    fn state_from_utc_date(&self, _utc: &NaiveDate) -> FixedOffset { self.clone() }
-    fn state_from_utc_time(&self, _utc: &NaiveTime) -> FixedOffset { self.clone() }
-    fn state_from_utc_datetime(&self, _utc: &NaiveDateTime) -> FixedOffset { self.clone() }
-}
-
-impl OffsetState for FixedOffset {
     fn local_minus_utc(&self) -> Duration { Duration::seconds(self.local_minus_utc as i64) }
 }
 

src/offset/local.rs

@@ -16,7 +16,7 @@ use naive::datetime::NaiveDateTime;
 use date::Date;
 use time::Time;
 use datetime::DateTime;
-use super::{Offset, LocalResult};
+use super::{TimeZone, LocalResult};
 use super::fixed::FixedOffset;
 
 /// Converts a `time::Tm` struct into the timezone-aware `DateTime`.
@@ -70,29 +70,29 @@ impl Local {
     }
 }
 
-impl Offset for Local {
-    type State = FixedOffset;
+impl TimeZone for Local {
+    type Offset = FixedOffset;
 
-    fn from_state(_state: &FixedOffset) -> Local { Local }
+    fn from_offset(_offset: &FixedOffset) -> Local { Local }
 
     // they are easier to define in terms of the finished date and time unlike other offsets
-    fn state_from_local_date(&self, local: &NaiveDate) -> LocalResult<FixedOffset> {
+    fn offset_from_local_date(&self, local: &NaiveDate) -> LocalResult<FixedOffset> {
         self.from_local_date(local).map(|&: date| *date.offset())
     }
-    fn state_from_local_time(&self, local: &NaiveTime) -> LocalResult<FixedOffset> {
+    fn offset_from_local_time(&self, local: &NaiveTime) -> LocalResult<FixedOffset> {
         self.from_local_time(local).map(|&: time| *time.offset())
     }
-    fn state_from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<FixedOffset> {
+    fn offset_from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<FixedOffset> {
         self.from_local_datetime(local).map(|&: datetime| *datetime.offset())
     }
 
-    fn state_from_utc_date(&self, utc: &NaiveDate) -> FixedOffset { 
+    fn offset_from_utc_date(&self, utc: &NaiveDate) -> FixedOffset {
         *self.from_utc_date(utc).offset()
     }
-    fn state_from_utc_time(&self, utc: &NaiveTime) -> FixedOffset {
+    fn offset_from_utc_time(&self, utc: &NaiveTime) -> FixedOffset {
         *self.from_utc_time(utc).offset()
     }
-    fn state_from_utc_datetime(&self, utc: &NaiveDateTime) -> FixedOffset {
+    fn offset_from_utc_datetime(&self, utc: &NaiveDateTime) -> FixedOffset {
         *self.from_utc_datetime(utc).offset()
     }
 

src/offset/mod.rs

@@ -3,21 +3,21 @@
 // See README.md and LICENSE.txt for details.
 
 /*!
- * Offsets from the local time to UTC.
+ * The time zone, which calculates offsets from the local time to UTC.
  *
- * There are three operations provided by the `Offset` trait:
+ * There are three operations provided by the `TimeZone` trait:
  *
- * 1. Converting the local `NaiveDateTime` to `DateTime<Offset>`
- * 2. Converting the UTC `NaiveDateTime` to `DateTime<Offset>`
- * 3. Converting `DateTime<Offset>` to the local `NaiveDateTime`
+ * 1. Converting the local `NaiveDateTime` to `DateTime<Tz>`
+ * 2. Converting the UTC `NaiveDateTime` to `DateTime<Tz>`
+ * 3. Converting `DateTime<Tz>` to the local `NaiveDateTime`
  *
- * 1 is used for constructors. 2 is used for the `with_offset` method of date and time types.
+ * 1 is used for constructors. 2 is used for the `with_timezone` method of date and time types.
  * 3 is used for other methods, e.g. `year()` or `format()`, and provided by an associated type
- * which implements `OffsetState` (which then passed to `Offset` for actual implementations).
- * Technically speaking `Offset` has a total knowledge about given timescale,
- * but `OffsetState` is used as a cache to avoid the repeated conversion
+ * which implements `Offset` (which then passed to `TimeZone` for actual implementations).
+ * Technically speaking `TimeZone` has a total knowledge about given timescale,
+ * but `Offset` is used as a cache to avoid the repeated conversion
  * and provides implementations for 1 and 3.
- * An `Offset` instance can be reconstructed from the corresponding `OffsetState` instance.
+ * An `TimeZone` instance can be reconstructed from the corresponding `Offset` instance.
  */
 
 use std::fmt;
@@ -70,13 +70,13 @@ impl<T> LocalResult<T> {
     }
 }
 
-impl<Off: Offset> LocalResult<Date<Off>> {
+impl<Tz: TimeZone> LocalResult<Date<Tz>> {
     /// Makes a new `DateTime` from the current date and given `NaiveTime`.
     /// The offset in the current date is preserved.
     ///
     /// Propagates any error. Ambiguous result would be discarded.
     #[inline]
-    pub fn and_time(self, time: NaiveTime) -> LocalResult<DateTime<Off>> {
+    pub fn and_time(self, time: NaiveTime) -> LocalResult<DateTime<Tz>> {
         match self {
             LocalResult::Single(d) => d.and_time(time)
                                        .map_or(LocalResult::None, LocalResult::Single),
@@ -89,7 +89,7 @@ impl<Off: Offset> LocalResult<Date<Off>> {
     ///
     /// Propagates any error. Ambiguous result would be discarded.
     #[inline]
-    pub fn and_hms_opt(self, hour: u32, min: u32, sec: u32) -> LocalResult<DateTime<Off>> {
+    pub fn and_hms_opt(self, hour: u32, min: u32, sec: u32) -> LocalResult<DateTime<Tz>> {
         match self {
             LocalResult::Single(d) => d.and_hms_opt(hour, min, sec)
                                        .map_or(LocalResult::None, LocalResult::Single),
@@ -104,7 +104,7 @@ impl<Off: Offset> LocalResult<Date<Off>> {
     /// Propagates any error. Ambiguous result would be discarded.
     #[inline]
     pub fn and_hms_milli_opt(self, hour: u32, min: u32, sec: u32,
-                             milli: u32) -> LocalResult<DateTime<Off>> {
+                             milli: u32) -> LocalResult<DateTime<Tz>> {
         match self {
             LocalResult::Single(d) => d.and_hms_milli_opt(hour, min, sec, milli)
                                        .map_or(LocalResult::None, LocalResult::Single),
@@ -119,7 +119,7 @@ impl<Off: Offset> LocalResult<Date<Off>> {
     /// Propagates any error. Ambiguous result would be discarded.
     #[inline]
     pub fn and_hms_micro_opt(self, hour: u32, min: u32, sec: u32,
-                             micro: u32) -> LocalResult<DateTime<Off>> {
+                             micro: u32) -> LocalResult<DateTime<Tz>> {
         match self {
             LocalResult::Single(d) => d.and_hms_micro_opt(hour, min, sec, micro)
                                        .map_or(LocalResult::None, LocalResult::Single),
@@ -134,7 +134,7 @@ impl<Off: Offset> LocalResult<Date<Off>> {
     /// Propagates any error. Ambiguous result would be discarded.
     #[inline]
     pub fn and_hms_nano_opt(self, hour: u32, min: u32, sec: u32,
-                            nano: u32) -> LocalResult<DateTime<Off>> {
+                            nano: u32) -> LocalResult<DateTime<Tz>> {
         match self {
             LocalResult::Single(d) => d.and_hms_nano_opt(hour, min, sec, nano)
                                        .map_or(LocalResult::None, LocalResult::Single),
@@ -157,20 +157,20 @@ impl<T: fmt::Debug> LocalResult<T> {
     }
 }
 
-/// The offset state.
-pub trait OffsetState: Sized + Clone + fmt::Debug {
-    /// Returns the offset from UTC to the local time stored in the offset state.
+/// The offset from the local time to UTC.
+pub trait Offset: Sized + Clone + fmt::Debug {
+    /// Returns the offset from UTC to the local time stored.
     fn local_minus_utc(&self) -> Duration;
 }
 
-/// The offset from the local time to UTC.
-pub trait Offset: Sized {
-    type State: OffsetState;
+/// The time zone.
+pub trait TimeZone: Sized {
+    type Offset: Offset;
 
-    /// Makes a new `Date` from year, month, day and the current offset.
+    /// Makes a new `Date` from year, month, day and the current time zone.
     /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
     ///
-    /// The offset normally does not affect the date (unless it is between UTC-24 and UTC+24),
+    /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
     /// but it will propagate to the `DateTime` values constructed via this date.
     ///
     /// Fails on the out-of-range date, invalid month and/or day.
@@ -178,10 +178,10 @@ pub trait Offset: Sized {
         self.ymd_opt(year, month, day).unwrap()
     }
 
-    /// Makes a new `Date` from year, month, day and the current offset.
+    /// Makes a new `Date` from year, month, day and the current time zone.
     /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
     ///
-    /// The offset normally does not affect the date (unless it is between UTC-24 and UTC+24),
+    /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
     /// but it will propagate to the `DateTime` values constructed via this date.
     ///
     /// Returns `None` on the out-of-range date, invalid month and/or day.
@@ -192,10 +192,10 @@ pub trait Offset: Sized {
         }
     }
 
-    /// Makes a new `Date` from year, day of year (DOY or "ordinal") and the current offset.
+    /// Makes a new `Date` from year, day of year (DOY or "ordinal") and the current time zone.
     /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
     ///
-    /// The offset normally does not affect the date (unless it is between UTC-24 and UTC+24),
+    /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
     /// but it will propagate to the `DateTime` values constructed via this date.
     ///
     /// Fails on the out-of-range date and/or invalid DOY.
@@ -203,10 +203,10 @@ pub trait Offset: Sized {
         self.yo_opt(year, ordinal).unwrap()
     }
 
-    /// Makes a new `Date` from year, day of year (DOY or "ordinal") and the current offset.
+    /// Makes a new `Date` from year, day of year (DOY or "ordinal") and the current time zone.
     /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
     ///
-    /// The offset normally does not affect the date (unless it is between UTC-24 and UTC+24),
+    /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
     /// but it will propagate to the `DateTime` values constructed via this date.
     ///
     /// Returns `None` on the out-of-range date and/or invalid DOY.
@@ -218,11 +218,11 @@ pub trait Offset: Sized {
     }
 
     /// Makes a new `Date` from ISO week date (year and week number), day of the week (DOW) and
-    /// the current offset.
+    /// the current time zone.
     /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
     /// The resulting `Date` may have a different year from the input year.
     ///
-    /// The offset normally does not affect the date (unless it is between UTC-24 and UTC+24),
+    /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
     /// but it will propagate to the `DateTime` values constructed via this date.
     ///
     /// Fails on the out-of-range date and/or invalid week number.
@@ -231,11 +231,11 @@ pub trait Offset: Sized {
     }
 
     /// Makes a new `Date` from ISO week date (year and week number), day of the week (DOW) and
-    /// the current offset.
+    /// the current time zone.
     /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
     /// The resulting `Date` may have a different year from the input year.
     ///
-    /// The offset normally does not affect the date (unless it is between UTC-24 and UTC+24),
+    /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
     /// but it will propagate to the `DateTime` values constructed via this date.
     ///
     /// Returns `None` on the out-of-range date and/or invalid week number.
@@ -246,14 +246,14 @@ pub trait Offset: Sized {
         }
     }
 
-    /// Makes a new `Time` from hour, minute, second and the current offset.
+    /// Makes a new `Time` from hour, minute, second and the current time zone.
     ///
     /// Fails on invalid hour, minute and/or second.
     fn hms(&self, hour: u32, min: u32, sec: u32) -> Time<Self> {
         self.hms_opt(hour, min, sec).unwrap()
     }
 
-    /// Makes a new `Time` from hour, minute, second and the current offset.
+    /// Makes a new `Time` from hour, minute, second and the current time zone.
     ///
     /// Returns `None` on invalid hour, minute and/or second.
     fn hms_opt(&self, hour: u32, min: u32, sec: u32) -> LocalResult<Time<Self>> {
@@ -263,7 +263,7 @@ pub trait Offset: Sized {
         }
     }
 
-    /// Makes a new `Time` from hour, minute, second, millisecond and the current offset.
+    /// Makes a new `Time` from hour, minute, second, millisecond and the current time zone.
     /// The millisecond part can exceed 1,000 in order to represent the leap second.
     ///
     /// Fails on invalid hour, minute, second and/or millisecond.
@@ -271,7 +271,7 @@ pub trait Offset: Sized {
         self.hms_milli_opt(hour, min, sec, milli).unwrap()
     }
 
-    /// Makes a new `Time` from hour, minute, second, millisecond and the current offset.
+    /// Makes a new `Time` from hour, minute, second, millisecond and the current time zone.
     /// The millisecond part can exceed 1,000 in order to represent the leap second.
     ///
     /// Returns `None` on invalid hour, minute, second and/or millisecond.
@@ -282,7 +282,7 @@ pub trait Offset: Sized {
         }
     }
 
-    /// Makes a new `Time` from hour, minute, second, microsecond and the current offset.
+    /// Makes a new `Time` from hour, minute, second, microsecond and the current time zone.
     /// The microsecond part can exceed 1,000,000 in order to represent the leap second.
     ///
     /// Fails on invalid hour, minute, second and/or microsecond.
@@ -290,7 +290,7 @@ pub trait Offset: Sized {
         self.hms_micro_opt(hour, min, sec, micro).unwrap()
     }
 
-    /// Makes a new `Time` from hour, minute, second, microsecond and the current offset.
+    /// Makes a new `Time` from hour, minute, second, microsecond and the current time zone.
     /// The microsecond part can exceed 1,000,000 in order to represent the leap second.
     ///
     /// Returns `None` on invalid hour, minute, second and/or microsecond.
@@ -301,7 +301,7 @@ pub trait Offset: Sized {
         }
     }
 
-    /// Makes a new `Time` from hour, minute, second, nanosecond and the current offset.
+    /// Makes a new `Time` from hour, minute, second, nanosecond and the current time zone.
     /// The nanosecond part can exceed 1,000,000,000 in order to represent the leap second.
     ///
     /// Fails on invalid hour, minute, second and/or nanosecond.
@@ -309,7 +309,7 @@ pub trait Offset: Sized {
         self.hms_nano_opt(hour, min, sec, nano).unwrap()
     }
 
-    /// Makes a new `Time` from hour, minute, second, nanosecond and the current offset.
+    /// Makes a new `Time` from hour, minute, second, nanosecond and the current time zone.
     /// The nanosecond part can exceed 1,000,000,000 in order to represent the leap second.
     ///
     /// Returns `None` on invalid hour, minute, second and/or nanosecond.
@@ -320,64 +320,64 @@ pub trait Offset: Sized {
         }
     }
 
-    /// Reconstructs the offset from the offset state.
-    fn from_state(state: &Self::State) -> Self;
+    /// Reconstructs the time zone from the offset.
+    fn from_offset(offset: &Self::Offset) -> Self;
 
-    /// Creates the offset state(s) for given local `NaiveDate` if possible.
-    fn state_from_local_date(&self, local: &NaiveDate) -> LocalResult<Self::State>;
+    /// Creates the offset(s) for given local `NaiveDate` if possible.
+    fn offset_from_local_date(&self, local: &NaiveDate) -> LocalResult<Self::Offset>;
 
-    /// Creates the offset state(s) for given local `NaiveTime` if possible.
-    fn state_from_local_time(&self, local: &NaiveTime) -> LocalResult<Self::State>;
+    /// Creates the offset(s) for given local `NaiveTime` if possible.
+    fn offset_from_local_time(&self, local: &NaiveTime) -> LocalResult<Self::Offset>;
 
-    /// Creates the offset state(s) for given local `NaiveDateTime` if possible.
-    fn state_from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<Self::State>;
+    /// Creates the offset(s) for given local `NaiveDateTime` if possible.
+    fn offset_from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<Self::Offset>;
 
     /// Converts the local `NaiveDate` to the timezone-aware `Date` if possible.
     fn from_local_date(&self, local: &NaiveDate) -> LocalResult<Date<Self>> {
-        self.state_from_local_date(local).map(|state| {
-            Date::from_utc(*local - state.local_minus_utc(), state)
+        self.offset_from_local_date(local).map(|offset| {
+            Date::from_utc(*local - offset.local_minus_utc(), offset)
         })
     }
 
     /// Converts the local `NaiveTime` to the timezone-aware `Time` if possible.
     fn from_local_time(&self, local: &NaiveTime) -> LocalResult<Time<Self>> {
-        self.state_from_local_time(local).map(|state| {
-            Time::from_utc(*local - state.local_minus_utc(), state)
+        self.offset_from_local_time(local).map(|offset| {
+            Time::from_utc(*local - offset.local_minus_utc(), offset)
         })
     }
 
     /// Converts the local `NaiveDateTime` to the timezone-aware `DateTime` if possible.
     fn from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<DateTime<Self>> {
-        self.state_from_local_datetime(local).map(|state| {
-            DateTime::from_utc(*local - state.local_minus_utc(), state)
+        self.offset_from_local_datetime(local).map(|offset| {
+            DateTime::from_utc(*local - offset.local_minus_utc(), offset)
         })
     }
 
-    /// Creates the offset state for given UTC `NaiveDate`. This cannot fail.
-    fn state_from_utc_date(&self, utc: &NaiveDate) -> Self::State;
+    /// Creates the offset for given UTC `NaiveDate`. This cannot fail.
+    fn offset_from_utc_date(&self, utc: &NaiveDate) -> Self::Offset;
 
-    /// Creates the offset state for given UTC `NaiveTime`. This cannot fail.
-    fn state_from_utc_time(&self, utc: &NaiveTime) -> Self::State;
+    /// Creates the offset for given UTC `NaiveTime`. This cannot fail.
+    fn offset_from_utc_time(&self, utc: &NaiveTime) -> Self::Offset;
 
-    /// Creates the offset state for given UTC `NaiveDateTime`. This cannot fail.
-    fn state_from_utc_datetime(&self, utc: &NaiveDateTime) -> Self::State;
+    /// Creates the offset for given UTC `NaiveDateTime`. This cannot fail.
+    fn offset_from_utc_datetime(&self, utc: &NaiveDateTime) -> Self::Offset;
 
     /// Converts the UTC `NaiveDate` to the local time.
     /// The UTC is continuous and thus this cannot fail (but can give the duplicate local time).
     fn from_utc_date(&self, utc: &NaiveDate) -> Date<Self> {
-        Date::from_utc(utc.clone(), self.state_from_utc_date(utc))
+        Date::from_utc(utc.clone(), self.offset_from_utc_date(utc))
     }
 
     /// Converts the UTC `NaiveTime` to the local time.
     /// The UTC is continuous and thus this cannot fail (but can give the duplicate local time).
     fn from_utc_time(&self, utc: &NaiveTime) -> Time<Self> {
-        Time::from_utc(utc.clone(), self.state_from_utc_time(utc))
+        Time::from_utc(utc.clone(), self.offset_from_utc_time(utc))
     }
 
     /// Converts the UTC `NaiveDateTime` to the local time.
     /// The UTC is continuous and thus this cannot fail (but can give the duplicate local time).
     fn from_utc_datetime(&self, utc: &NaiveDateTime) -> DateTime<Self> {
-        DateTime::from_utc(utc.clone(), self.state_from_utc_datetime(utc))
+        DateTime::from_utc(utc.clone(), self.offset_from_utc_datetime(utc))
     }
 }
 

src/offset/utc.rs

@@ -15,10 +15,10 @@ use naive::time::NaiveTime;
 use naive::datetime::NaiveDateTime;
 use date::Date;
 use datetime::DateTime;
-use super::{Offset, OffsetState, LocalResult};
+use super::{TimeZone, Offset, LocalResult};
 
-/// The UTC offset. This is the most efficient offset when you don't need the local time.
-/// It is also used as an offset state (which is also a dummy type).
+/// The UTC time zone. This is the most efficient time zone when you don't need the local time.
+/// It is also used as an offset (which is also a dummy type).
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub struct UTC;
 
@@ -34,27 +34,27 @@ impl UTC {
     }
 }
 
+impl TimeZone for UTC {
+    type Offset = UTC;
+
+    fn from_offset(_state: &UTC) -> UTC { UTC }
+
+    fn offset_from_local_date(&self, _local: &NaiveDate) -> LocalResult<UTC> {
+        LocalResult::Single(UTC)
+    }
+    fn offset_from_local_time(&self, _local: &NaiveTime) -> LocalResult<UTC> {
+        LocalResult::Single(UTC)
+    }
+    fn offset_from_local_datetime(&self, _local: &NaiveDateTime) -> LocalResult<UTC> {
+        LocalResult::Single(UTC)
+    }
+
+    fn offset_from_utc_date(&self, _utc: &NaiveDate) -> UTC { UTC }
+    fn offset_from_utc_time(&self, _utc: &NaiveTime) -> UTC { UTC }
+    fn offset_from_utc_datetime(&self, _utc: &NaiveDateTime) -> UTC { UTC}
+}
+
 impl Offset for UTC {
-    type State = UTC;
-
-    fn from_state(_state: &UTC) -> UTC { UTC }
-
-    fn state_from_local_date(&self, _local: &NaiveDate) -> LocalResult<UTC> {
-        LocalResult::Single(UTC)
-    }
-    fn state_from_local_time(&self, _local: &NaiveTime) -> LocalResult<UTC> {
-        LocalResult::Single(UTC)
-    }
-    fn state_from_local_datetime(&self, _local: &NaiveDateTime) -> LocalResult<UTC> {
-        LocalResult::Single(UTC)
-    }
-
-    fn state_from_utc_date(&self, _utc: &NaiveDate) -> UTC { UTC }
-    fn state_from_utc_time(&self, _utc: &NaiveTime) -> UTC { UTC }
-    fn state_from_utc_datetime(&self, _utc: &NaiveDateTime) -> UTC { UTC}
-}
-
-impl OffsetState for UTC {
     fn local_minus_utc(&self) -> Duration { Duration::zero() }
 }
 

src/time.rs

@@ -11,44 +11,44 @@ use std::cmp::Ordering;
 use std::ops::{Add, Sub};
 
 use Timelike;
-use offset::{Offset, OffsetState};
+use offset::{TimeZone, Offset};
 use duration::Duration;
 use naive::time::NaiveTime;
 use format::DelayedFormat;
 
 /// ISO 8601 time with timezone.
 #[derive(Clone)]
-pub struct Time<Off: Offset> {
+pub struct Time<Tz: TimeZone> {
     time: NaiveTime,
-    offset: Off::State,
+    offset: Tz::Offset,
 }
 
-impl<Off: Offset> Time<Off> {
+impl<Tz: TimeZone> Time<Tz> {
     /// Makes a new `Time` with given *UTC* time and offset.
-    /// The local time should be constructed via the `Offset` trait.
+    /// The local time should be constructed via the `TimeZone` trait.
     //
     // note: this constructor is purposedly not named to `new` to discourage the direct usage.
     #[inline]
-    pub fn from_utc(time: NaiveTime, offset: Off::State) -> Time<Off> {
+    pub fn from_utc(time: NaiveTime, offset: Tz::Offset) -> Time<Tz> {
         Time { time: time, offset: offset }
     }
 
-    /// Retrieves an associated offset.
+    /// Retrieves an associated offset from UTC.
     #[inline]
-    pub fn offset<'a>(&'a self) -> &'a Off::State {
+    pub fn offset<'a>(&'a self) -> &'a Tz::Offset {
         &self.offset
     }
 
-    /// Retrieves an associated offset.
+    /// Retrieves an associated time zone.
     #[inline]
-    pub fn timezone(&self) -> Off {
-        Offset::from_state(&self.offset)
+    pub fn timezone(&self) -> Tz {
+        TimeZone::from_offset(&self.offset)
     }
 
-    /// Changes the associated offset.
+    /// Changes the associated time zone.
     /// This does not change the actual `Time` (but will change the string representation).
     #[inline]
-    pub fn with_timezone<Off2: Offset>(&self, tz: &Off2) -> Time<Off2> {
+    pub fn with_timezone<Tz2: TimeZone>(&self, tz: &Tz2) -> Time<Tz2> {
         tz.from_utc_time(&self.time)
     }
 
@@ -66,12 +66,12 @@ impl<Off: Offset> Time<Off> {
 }
 
 /// Maps the local time to other time with given conversion function.
-fn map_local<Off: Offset, F>(t: &Time<Off>, mut f: F) -> Option<Time<Off>>
+fn map_local<Tz: TimeZone, F>(t: &Time<Tz>, mut f: F) -> Option<Time<Tz>>
         where F: FnMut(NaiveTime) -> Option<NaiveTime> {
     f(t.naive_local()).and_then(|time| t.timezone().from_local_time(&time).single())
 }
 
-impl<Off: Offset> Time<Off> where Off::State: fmt::Display {
+impl<Tz: TimeZone> Time<Tz> where Tz::Offset: fmt::Display {
     /// Formats the time in the specified format string.
     /// See the `format` module on the supported escape sequences.
     #[inline]
@@ -80,29 +80,29 @@ impl<Off: Offset> Time<Off> where Off::State: fmt::Display {
     }
 }
 
-impl<Off: Offset> Timelike for Time<Off> {
+impl<Tz: TimeZone> Timelike for Time<Tz> {
     #[inline] fn hour(&self) -> u32 { self.naive_local().hour() }
     #[inline] fn minute(&self) -> u32 { self.naive_local().minute() }
     #[inline] fn second(&self) -> u32 { self.naive_local().second() }
     #[inline] fn nanosecond(&self) -> u32 { self.naive_local().nanosecond() }
 
     #[inline]
-    fn with_hour(&self, hour: u32) -> Option<Time<Off>> {
+    fn with_hour(&self, hour: u32) -> Option<Time<Tz>> {
         map_local(self, |time| time.with_hour(hour))
     }
 
     #[inline]
-    fn with_minute(&self, min: u32) -> Option<Time<Off>> {
+    fn with_minute(&self, min: u32) -> Option<Time<Tz>> {
         map_local(self, |time| time.with_minute(min))
     }
 
     #[inline]
-    fn with_second(&self, sec: u32) -> Option<Time<Off>> {
+    fn with_second(&self, sec: u32) -> Option<Time<Tz>> {
         map_local(self, |time| time.with_second(sec))
     }
 
     #[inline]
-    fn with_nanosecond(&self, nano: u32) -> Option<Time<Off>> {
+    fn with_nanosecond(&self, nano: u32) -> Option<Time<Tz>> {
         map_local(self, |time| time.with_nanosecond(nano))
     }
 
@@ -110,55 +110,55 @@ impl<Off: Offset> Timelike for Time<Off> {
     fn num_seconds_from_midnight(&self) -> u32 { self.naive_local().num_seconds_from_midnight() }
 }
 
-impl<Off: Offset, Off2: Offset> PartialEq<Time<Off2>> for Time<Off> {
-    fn eq(&self, other: &Time<Off2>) -> bool { self.time == other.time }
+impl<Tz: TimeZone, Tz2: TimeZone> PartialEq<Time<Tz2>> for Time<Tz> {
+    fn eq(&self, other: &Time<Tz2>) -> bool { self.time == other.time }
 }
 
-impl<Off: Offset> Eq for Time<Off> {
+impl<Tz: TimeZone> Eq for Time<Tz> {
 }
 
-impl<Off: Offset> PartialOrd for Time<Off> {
-    fn partial_cmp(&self, other: &Time<Off>) -> Option<Ordering> {
+impl<Tz: TimeZone> PartialOrd for Time<Tz> {
+    fn partial_cmp(&self, other: &Time<Tz>) -> Option<Ordering> {
         self.time.partial_cmp(&other.time)
     }
 }
 
-impl<Off: Offset> Ord for Time<Off> {
-    fn cmp(&self, other: &Time<Off>) -> Ordering { self.time.cmp(&other.time) }
+impl<Tz: TimeZone> Ord for Time<Tz> {
+    fn cmp(&self, other: &Time<Tz>) -> Ordering { self.time.cmp(&other.time) }
 }
 
-impl<Off: Offset, H: hash::Hasher + hash::Writer> hash::Hash<H> for Time<Off> {
+impl<Tz: TimeZone, H: hash::Hasher + hash::Writer> hash::Hash<H> for Time<Tz> {
     fn hash(&self, state: &mut H) { self.time.hash(state) }
 }
 
-impl<Off: Offset> Add<Duration> for Time<Off> {
-    type Output = Time<Off>;
+impl<Tz: TimeZone> Add<Duration> for Time<Tz> {
+    type Output = Time<Tz>;
 
-    fn add(self, rhs: Duration) -> Time<Off> {
+    fn add(self, rhs: Duration) -> Time<Tz> {
         Time { time: self.time + rhs, offset: self.offset }
     }
 }
 
-impl<Off: Offset, Off2: Offset> Sub<Time<Off2>> for Time<Off> {
+impl<Tz: TimeZone, Tz2: TimeZone> Sub<Time<Tz2>> for Time<Tz> {
     type Output = Duration;
 
-    fn sub(self, rhs: Time<Off2>) -> Duration { self.time - rhs.time }
+    fn sub(self, rhs: Time<Tz2>) -> Duration { self.time - rhs.time }
 }
 
-impl<Off: Offset> Sub<Duration> for Time<Off> {
-    type Output = Time<Off>;
+impl<Tz: TimeZone> Sub<Duration> for Time<Tz> {
+    type Output = Time<Tz>;
 
     #[inline]
-    fn sub(self, rhs: Duration) -> Time<Off> { self.add(-rhs) }
+    fn sub(self, rhs: Duration) -> Time<Tz> { self.add(-rhs) }
 }
 
-impl<Off: Offset> fmt::Debug for Time<Off> {
+impl<Tz: TimeZone> fmt::Debug for Time<Tz> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:?}{:?}", self.naive_local(), self.offset)
     }
 }
 
-impl<Off: Offset> fmt::Display for Time<Off> where Off::State: fmt::Display {
+impl<Tz: TimeZone> fmt::Display for Time<Tz> where Tz::Offset: fmt::Display {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}{}", self.naive_local(), self.offset)
     }