Deno: std/datetime: day of year test fails in certain timezones

[wperron]

I'm in the east coast timezone and the dayOfYear test from std/datetime fails on the first assertion (aka it thinks January 1st 00:00 is December 31st). Changing the timezone on my machine fixes the issue.

[lucacasonato]

cc @timreichen

[wperron]

Did some digging, I _think_ it has to do with the fact that we use getFullYear instead of getUTCFullYear to compare the date with Jan 1st of the same year. I did some tests locally and that seemed to fix the problem, but I got stuck because the fix broke the tests for 400 BC

[timreichen]

I am on it. @wperron: you are right. getUTCFullYear fixes the problem.
The 400 BC test is broken, because a zero is missing. new Date("-00400-01-01") gets parsed to year 400 instead of -400. new Date("-000400-01-01") works as expected.
PR #7466

[wperron]

@timreichen I noticed it that too actually, I figured if it was -00400 it was probably right 😅 I should've just asked

[timreichen]

PR is merged. I think this issue can be closed.

[j4qfrost]

https://github.com/denoland/deno/pull/7726 this is a slightly more robust way of resolving the timezone issue.