I’ve noticed that on some devices the NSTimeZone‘s name method for a particular timezone can return different values. When testing the Brisbane time zone, my device returns @"Australia/Brisbane" whereas another user’s device returns "Etc/GMT-10". Both iPhone’s are running 3.1.2.
The Date and Time Programming Guide for Cocoa states that:
timeZoneWithName: The name passed to this method may be in any of the
formats understood by the system, for
example EST, Etc/GMT-2,
America/Argentina/Buenos_Aires,
Europe/Monaco, or US/Pacific, as shown
in the following code fragment.
I’d just like to know what could determine which value is used? The device? The language?
I’ve discovered what the reason for this was.
When manually setting the timezone from Apple’s build-in list, the correct and exact timezone name is returned. However, some mobile carriers provide the current time zone offset over the air, and if this is the case, Apple provide an “Automatic” setting which allows the iPhone to change time zone automatically when they move across into another time zone.
The problem is that while the current GMT offset is provided, there’s no way to tell what latitude the user is at. Obviously, there may be for example, several cities in Australia with the a time zone of GMT -10. Therefore, no specific time zone name is available, only that the phone is currently GMT -10.