Question

With the following code, foo gives me the local time or GMT?

NSString * foo = [formatter2 stringFromDate:[NSDate dateWithTimeIntervalSinceNow:-2 * 3600]];  

Answer 1

The string flyerid will represent the time minus 2 hours in your current time zone, yes. That’s the purpose of the date formatter, which, by default, uses the computer’s Locale information to convert a passed-in date to the representation closest to what the user expects. That includes using the computer’s time zone. (You can change that, of course, by sending setTimeZone: to the formatter.)

The date object itself has no time zone. It is only a moment in time, whose description or representation varies depending on where on the globe you are. For example, the moment when John Lennon was pronounced dead is represented in its local time (GMT-5) as 8 December, 1980, 11:15 AM, but over on the West coast of the US, that’s 8:15 AM, and in Lennon’s place of birth, it’s 4:15 in the afternoon. He was only pronounced dead once, though — same moment, different ways of reading it.