Include function to fetch timezone offset for certain date

[chexxor]

This comes from a discussion in the Slack chatroom.

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natefaubion
If you have a timezone offset, you can adjust the datetime before giving it to formatters
Maybe something should be in purescript-now for getting the current user timezone offset

The time zone offset returned is the one that applies for the Date that it’s called on. Where the host system is configured for daylight saving, the offset will change depending on the date and time that the Date represents and that daylight saving applies.

Right, so it has to be for the date you give it
Yeah, I doubt anything in PS is going to exist for that natively
But it seems to me like something that could exist in purescript-now, given an instant, get the user’s timezone offset
I say purescript-now, because it’s the only effectful date agnostic library

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Full thread:

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unisay [8:25 AM]
How to format DateTime such that user sees time in his own timezone? I looked at purescript-formatters but there is no TimeZone support - its all UTC; Please advise

hdgarrood [8:26 AM]
it's possible that there just isn't a purescript library for this
we're using bindings to moment.js at lumi

dariooddenino [8:27 AM]
Yeah, I'm using FFI and luxon.js

unisay [8:27 AM]
@hdgarrood we also use moment.js at collegevine (but from inside of JSX), are your bindings open-sourced?

hdgarrood [8:27 AM]
don't think so unfortunately

unisay [8:28 AM]
@dariooddenino do you happen to have it as a library?

dariooddenino [8:28 AM]
No, I just wrapped a handful of functions I'm using
it's not a lot of work though

unisay [8:28 AM]
Thanks to y’all

dariooddenino [8:29 AM]
I can put up a gist if you want, but it's not very safe code 😄

natefaubion [8:32 AM]
If you have a timezone offset, you can adjust the datetime before giving it to formatters
Maybe something should be in purescript-now for getting the current user timezone offset (edited)

dariooddenino [8:33 AM]
and then daylight saving times come to bite you

natefaubion [8:35 AM]
Does the JS date machinery not account for that given the current time?

The time zone offset returned is the one that applies for the Date that it’s called on. Where the host system is configured for daylight saving, the offset will change depending on the date and time that the Date represents and that daylight saving applies.

Right, so it has to be for the date you give it
Yeah, I doubt anything in PS is going to exist for that natively
But it seems to me like something that could exist in purescript-now, given an instant, get the user’s timezone offset
I say purescript-now, because it’s the only effectful date agnostic library

[Cmdv]

was going to do this quickly, is it a case of doing an FFI to getTimezoneOffset?

[thomashoneyman]

Yes, from my reading of this chat thread that's the best bet.

[Cmdv]

@thomashoneyman cool I'll add it 😄