Question

What is the Objective-C equivalent of the Java TimeZone class?

Answer 1

NSTimeZone, I believe. Can’t say I’ve ever done any Objective-C myself, but it looks right…

Apple also has a (pretty short) article on using it.

It’s quite likely that they won’t be direct equivalents in every respect, of course… but if there’s something you would use with Java’s TimeZone which you can’t figure out in NSTimeZone, ask about that specific call… and someone else can help you, I’m sure 🙂

EDIT: The purpose of a time zone class is to convert between local times in different time zones. For example, right now, it’s 7.50pm for me – but it’s 12.50pm for the person who I’m about to have a Skype call with. One option for representing dates and times is to always store them in UTC (which is sort of the “zero” of time zones) and then convert the UTC value into the “local” time for the user, e.g. for display purposes. That’s not always the right option, but it’s usually a good starting point.

At other times, you may have a local time and know person X’s time zone – and want to convert it to person Y’s time zone. It’s usually easiest to do that by converting the local time to UTC (using X’s time zone) and then to convert it back to local time using Y’s time zone.

Time zones aren’t nearly as straightforward as you might expect – mostly due to daylight savings. Oddities:

• Local times which either don’t exist, or occur twice, due to DST transitions
• Time zones which change to DST at midnight, so that midnight doesn’t always exist
• Governments deciding to scrap (or introduce) DST at almost no notice
• DST which isn’t the normal “move an hour forwards”. IIRC, Tibet was considering introducing DST of 1:15.
• Historical changes to time zones

The list goes on.