NSDate - Convert Date to GMT

Question

I need the ability to convert an NSDate value to a GMT Date.

How can I go about converting an NSDate value to a GMT formatted NSDate<

Answer 1

Working with time in Cocoa can be complicated. When you get an NSDate object, it's in the local time zone. [[NSTimeZone defaultTimeZone] secondsFromGMT] gives you the offset of the current time zone from GMT. Then you can do this:

NSDate *localDate = // get the date
NSTimeInterval timeZoneOffset = [[NSTimeZone defaultTimeZone] secondsFromGMT]; // You could also use the systemTimeZone method
NSTimeInterval gmtTimeInterval = [localDate timeIntervalSinceReferenceDate] - timeZoneOffset;
NSDate *gmtDate = [NSDate dateWithTimeIntervalSinceReferenceDate:gmtTimeInterval];

Now gmtDate should have the correct date in GMT for you. In order to display it, look at NSDateFormatter, specifically the setDateStyle and setTimeStyle methods. You create an NSDateFormatter, configure it the way you want, and then call stringFromDate: to get a nicely formatted string.