fix(datetime/day_of_year): respect time zone of date

[familyboat]

Maybe fix #1114

[kt3k]

I'm not sure #1114 is a 'bug'.

Does it make sense to have both UTC and local timezone versions of APIs (like #3295 ) ?

[familyboat]

You can specify time zone in two ways.

1. Specify it in date string (e.g.: new Date("2023-01-01T00:00:00.000+08:00)).

2. Do not specify it explicitly, which means Date will use your local time zone.

But there are some cases where you cannot get result what you want.

const firstDay = new Date("2023-01-01T00:00:00.000+09:00"); // first day in year 2023 in east 9th district
console.log(firstDay.getFullYear()) // 2022, my local time zone is east 8th district

Maybe it is not a bug.

[familyboat]

When Intantiating Date with different arguments, the time zone of date varies. Some is utc time zone, some is your local time zone, some is your specified time zone, which will be converted to your local time zone. See more information in https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date#date_time_string_format.
In this line https://github.com/denoland/deno_std/blob/aea85151e872338f9d6c52041e58ed14fbf21650/datetime/day_of_year.ts#L13 , the time zone of date is your local time zone, so the reault may be 70, or 69.
Here what I want to say is that developer should know the time zone of date instance, and time zone used in dayOfYear should be pointed out in docs. Leave the responsibility to the developer.

[kt3k]

Utc in the middle of dayOfYear sounds strange to me. How about utcDayOfYear or dayOfYearUtc?

[familyboat]

I prefer dayOfYearUtc. Updated.

[kt3k]

LGTM