This may sound strange, but the final type for the offset "value" was
originally `time::Duration` (returned by `Offset::local_minus_utc`).
This caused a lot of problems becaus adding `Duration` fully interacts
with leap seconds and `Duration` itself is somewhat deprecated.
This commit entirely replaces this role of `Duration` with
`FixedOffset`. So if we had `Offset` and `Duration` to represent
the "storage" offset type and the offset "value" in the past,
we now have `Offset` and `FixedOffset`. Storage-to-value conversion is
called to "fix" the offset---an apt term for the type.
The list of actual changes:
- The time zone offset is now restricted to UTC-23:59:59 through
UTC+23:59:59, and no subsecond value is allowed. As described above,
`FixedOffset` is now fully used for this purpose.
- One can now add and subtract `FixedOffset` to/from timelike values.
Replaces a temporary `chrono::offset::add_with_leapsecond` function.
Datelike & non-timelike values are never affected by the offset.
- UTC and local views to `Date<Tz>` are now identical. We keep
relevant methods for the consistency right now.
- `chrono::format::format` now receives `FixedOffset` in place of
`(Old)Duration`.
- `Offset` now has a `fix` method to resolve, or to "fix" the
"storage" offset (`Offset`) to the offset "value" (`FixedOffset`).
- `FixedOffset::{local_minus_utc, utc_minus_local}` methods are added.
They no longer depend on `Duration` as well.
Due to the backward compatibility we won't be going to remove support
for `time::Duration` in 0.3, and the initial 0.3.0 release won't have
proper `std::time::Duration` support (haven't finalized the logics).
However we will reserve proper names and signatures for the upcoming
`std::time::Duration` support---the "older" duration type will be
referred as "signed" in the names.
- Added a `chrono::prelude` module. This does not have the (old)
`Duration` type reexported, so the documentation has now correctly
replaced all occurrences of `chrono::Duration`. The existing
`chrono::Duration` reexport itself remains for the compatibility.
- Avoided using a plain `Duration` type in the signature, to avoid
any ambiguity.
- Renamed `checked_{add,sub}` to `checked_{add,sub}_signed`.
- Subtraction operator between two instants has been removed and
replaced with `signed_duration_since`. This follows the naming
chosen by `std::time::SystemTime` etc., and the version for newer
`std::time::Duration` will be named to `duration_since`.
- Feature flags are now required on the doctests.
- New lints for trivial casts. We are now not going to change
the internal implementation type for `NaiveDate`, so that's fine.
this is partly because... we are using the simple name `timestamp`
in the `Parsed` anyway. that value is so widespread enough that
its name can be simply THE timestamp. old methods have been marked
deprecated.
this is most importantly required for negative years in `Parsed`,
which the current parser doesn't generate but is nevertheless
possible in principle. also updates tests for new fields.
this new module encompasses John Nagle's original RFC 2822 and 3337
parsers, updated to fully compatible to the actual standard.
the contributed `parse` module has been merged into it.
Kang Seonghoon
János Illés
Jisoo Park