timezone select

[georgehrke]

fixes #586

[georgehrke]

This small change has actually a big impact. I'm considering doing a 1.6.1 beta before the final release.

[tcitworld]

I don't see right away what it does, I'll check later.

[georgehrke]

It all comes down to one difference:

• the JS date object stores date and time in relation to an offset.
• the string representation just stores date and time.

Let's say your browser's UTC offset is one hour and so is the offset of the timezone you selected: both will work and the event will be displayed correctly.

But let's say your browser's UTC offset is one hour, but you selected New York as your timezone, then you will still see the event with the one hour UTC difference, although you would expect it to be displayed in New York timezone.

That's because when invoking the convertZone method on ICAL.Time, the offset of the js date object is updated as well.

If you have an js date object like this:
2018-02-27 18:00 UTC+1
converting to New York timezone results in
2018-02-27 12:00 UTC-5

Now your browser wants to display it, but knows you are not in UTC-5 but in UTC+1, so it adds the 6 hours again and you end up with 2018-02-27 18:00

[tcitworld]

Thx :)

[georgehrke]

@tcitworld Did you have time to review this yet? :)