Closes #13972
# Description
First commit: a hotfix concerning my last PR #15544! I had a
``unwrap_or_default`` that resulted in all years before ~1800 being
considered as "now", because the ``num_nanoseconds()`` overflowed.
Cc @fdncred
Second: about #13972
Negative years are not allowed with RFC 2822 formatting, so I fallback
RTC 3339 in such cases.
If you want you might Rebase and Merge, and not squash.
# User-Facing Changes
On master 🔴 :
```nu
~> {year: 1900} | into datetime
Mon, 1 Jan 1900 00:00:00 +0200 (125 years ago)
# OK
~> {year: 1000} | into datetime
Wed, 1 Jan 1000 00:00:00 +0200 (now)
# NOT OK: now?
~> {year: -1000} | into datetime
-1000-01-01T00:00:00+02:00 (now)
# NOT OK: now?
~> {year: -1000} | into datetime | format date
Error: × Main thread panicked.
├─▶ at C:\Users\RIL1RT\.cargo\registry\src\index.crates.io-6f17d22bba15001f\chrono-0.4.39\src\datetime\mod.rs:626:14
╰─▶ writing rfc2822 datetime to string should never fail: Error
help: set the `RUST_BACKTRACE=1` environment variable to display a backtrace.
# NOT OK: panics
```
On this branch 🟢 :
```nu
~> {year: 1900} | into datetime
Mon, 1 Jan 1900 00:00:00 +0200 (in 125 years)
~> {year: 1000} | into datetime
Wed, 1 Jan 1000 00:00:00 +0200 (1025 years ago)
~> {year: -1000} | into datetime
-1000-01-01T00:00:00+02:00 (3025 years ago)
~> {year: -1000} | into datetime | format date
-1000-01-01T00:00:00+02:00
~> '3000 years ago' | date from-human | format date
-0975-04-11T18:18:24.301641100+02:00
```
# Tests + Formatting
# After Submitting
Nothing required IMO
c8c018452f