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soundcraft/apps
Dylan M. Taylor d47abe484d Use chrono instead of hand-rolled UTC conversion (#844)
* Use chrono for UTC/calendar conversion instead of hand-rolled copies

Replaces the civil_from_days copy behind the desktop app's log timestamp with
chrono as a workspace dependency. The output format is unchanged and pinned by
the existing test. AGENTS.md now says time goes through chrono.

Follow-up to storytold/cadcraft#1785

* Never panic logging on a clock outside chrono's range

chrono's From<SystemTime> unwraps internally, so a clock past year 262143
panicked inside the logger. timestamp now reads the duration since the epoch
and goes through the fallible DateTime::from_timestamp, reading an
out-of-range clock as the epoch, exactly as the pre-epoch clamp already did.
The year is written with {:04} rather than %Y, which would prefix a '+' past
year 9999. Tests cover the far-future and year-10000 cases.

* Don't build an unrepresentable SystemTime in the far-future test

UNIX_EPOCH + Duration::from_secs(u64::MAX / 2) overflows Windows'
SystemTime and panicked before timestamp() ran, failing the Windows
test job. Build it with checked_add and only assert where it exists.

* time: preserve old out-of-range log timestamp (no epoch fallback)

`DateTime::from_timestamp(...).unwrap_or_default()` silently reset any clock
past chrono's year range to 1970-01-01, changing output the old hand-rolled
`civil_from_days` converted exactly. Restore the old conversion domain with a
cycle-based helper that routes the calendar through chrono (the calendar
repeats every 400 years = 146_097 days, so month/day/time come from chrono and
only the year is carried in i128, keeping every i64 exact). Keep the pre-1970
epoch clamp; u64 seconds past i64::MAX saturate rather than falling back.

Pinned old outputs in the test (replacing the u64::MAX/2 -> epoch assertion):
  u64::MAX/2 s -> 292277026596-12-04T15:30:07.000Z
  10_000_000_000_000 s -> 318857-05-20T17:46:40.000Z

* Don't build a year-318857 SystemTime unchecked in the logging test

Windows' SystemTime only reaches about year 30828, so
UNIX_EPOCH + Duration::from_secs(10_000_000_000_000) panicked before
timestamp() ran and failed the Windows test job. Build it with
checked_add and assert where the platform can hold it. The year-10000
case fits everywhere and stays unconditional.

* Name the 400-year range extension as the one exception to the time rule

The rule said never to hand-roll calendar math, but the range fix
(shifting by whole 400-year Gregorian cycles so dates past chrono's year
range keep their old output) is cycle arithmetic, so the rule and the code
disagreed. The rule now names that exception: the library still computes
month, day and time, and only whole cycles are carried in the year.

* Say the library computes month and day; time-of-day is plain arithmetic

Narrows the range-extension wording: the date library computes the
calendar fields, and splitting seconds into hours, minutes and seconds
is ordinary arithmetic, which is what the code does.
2026-10-23 11:35:06 -04:00
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