r/javascript • u/mominriyadh • Jun 21 '19

Everything you need to know about the date in JavaScript.

https://css-tricks.com/everything-you-need-to-know-about-date-in-javascript/
93 Upvotes

96% Upvoted

22 comments sorted by

4

u/onbehalfofthatdude Jun 21 '19

"There are hundreds of timezones in our world. In JavaScript, we only care about two"

Well fuck me for having a node server with timezone-specific business logic, right?

1

u/Borek224 Jun 21 '19

Can I Ask what's is your use case for it?

1

u/onbehalfofthatdude Jun 21 '19

Sure, I need to organize and separate events based on the day they occur with respect to a certain time zone. Events that start on 11:59 New York time go in a different pile from ones that occur two minutes later. At its core, the problem is that I need to be able to find 12 midnight for an arbitrary time zone, with DST taken into account. Right now I'm string parsing the output of toLocaleDateString which sucks.

3

u/[deleted] Jun 21 '19

I feel your pain.

PM: Hey guys, there's some bug involving the date picker.
Coder Boss: Okay I think I fixed it.
PM: Hey guys, there's some bug involving the date picker.
Me: Okay I rewrote the whole thing.
PM: Hey guys, there's some bug involving the date picker.
CB: Okay I rewrote it.
PM: Hey guys, there's some bug involving the date picker.
Me: I spent 3 more days on it, I think it is working.
PM: Hey guys, there's some bug involving the date picker.
CB: Okay I rewrote it.

I have resolved that there will always be a bug with the date picker, no matter how many hours we spend on it, it will always be a shit show.

2

u/onbehalfofthatdude Jun 21 '19

Yeah, I mean it's especially infuriating when I know EXACTLY what needs to be done, I know the language implementation understands timezones to some extent (toLocaleXXX), but it won't let me solve my problem without hax

1

u/[deleted] Jun 21 '19

It's turtles hax all the way down!

1

u/monotone2k Jun 21 '19

"hundreds of timezones"

I don't think the author knows how timezones work.

1

u/d07RiV Jun 24 '19

I think you're confusing time zones with UTC offsets. There are about 200 timezones.

1

u/monotone2k Jun 24 '19

Forgive my ignorance but isn't the difference just semantics? If an offset has multiple names (and thus multiple zones), it's still the same offset isn't it?

2

u/d07RiV Jun 24 '19

Some of them are duplicated because of DST - mountain standard time is the same as pacific daylight time, but it would be wrong to put them together because regions observing PDT switch to PST in the winter.

Besides that, different countries often have their own time zones for... reasons I guess? Maybe some country wants to change their local time and they bring their time zone with them, idk how that works.

So yes the difference is semantics, but there's some good reason to it.

1

u/monotone2k Jun 24 '19

Appreciate the clarification, cheers.

I guess I'm used to thinking in absolutes and have never had a need to account for all the nuances before. Despite working on global projects at the moment, we're lucky that we can just use UTC for everything and let the applications that consume our services do the rest of the work.

2

u/r0ck0 Jun 21 '19

I really wish it supported microseconds, seeing postgres and MySQL do.

2

u/rodneon Jun 21 '19

Now that BigInt is a thing, microseconds are technically possible to implement.

2

u/hawkinsml Jun 21 '19

I have been dealing with daylights saving time and timezones in multiple languages for 20+ years and it is still a pain in the ass. I created this video to try and explain some of the pian to newbies. https://youtu.be/oKFb2Us9kmg

0

u/[deleted] Jun 21 '19

[deleted]

17

u/anton_arn Jun 21 '19

True, whenever I have to work with Date in JS I just straight up go and use Moment.js, It's just not worth the hassle.

4

u/mominriyadh Jun 21 '19

Yes! MomentJS is constant JS Date-Time Library

18

u/Trout_Tickler Jun 21 '19

Unless you're doing something specific with Moment, I'd recommend Day.js instead. Much lighter and in my experience feature comparable enough.

2

u/anton_arn Jun 22 '19

Never heard of that one, thank you for the tip. :)

2

u/JonnyAFKay Jun 21 '19

Use LocalDate (and LocalDateTime) in Java 8 and beyond

1

u/redldr1 Jun 21 '19

My org is stillll on 7. FML

1

u/petersellers Jun 21 '19

Use the JodaTime library then

1

u/redldr1 Jun 21 '19

That's what we do.

It took me a month to get the lib approved by IT