What NSTimeZone value does an NSDateFormatter use if you don't pass it in?

Question

What NSTimeZone value does an NSDateFormatter use if you don't pass it in? I'd like to either use the default timeZone value, or pass in a given one. I'd like to do something like this:

- (NSString *) announcementTime{
    NSTimeZone *defaultTimeZone;  // What does this become?
    [self announcementTimeInTimeZone:defaultTimeZone];
}

- (NSString *) announcementTimeInTimeZone:(NSTimeZone *)timeZone{

  NSDateFormatter *formatter = [[NSDateFormatter alloc] init];

  [formatter setDateStyle:NSDateFormatterNoStyle];
  [formatter setTimeStyle:NSDateFormatterShortStyle];
  [formatter setTimeZone:timeZone];

  return time;
}

What time zone do I want to pass in to my announcementTimeInTimeZone: method? Perhaps [NSTimeZone defaultTimeZone] or [NSTimeZone localTimeZone]. I'm just not sure what the default is and don't see it documented anywhere.

Answer 1

I could not find any documentation either but I had a play in the debugger and it looks like NSDateFormatter uses defaultTimeZone.

(lldb) p (NSTimeZone*)[f timeZone] (NSTimeZone *) $1 = 0x0a926fa0 @"Australia/Sydney"

(lldb) p (NSTimeZone*)[NSTimeZone defaultTimeZone] (NSTimeZone *) $2 = 0x0a926fa0 @"Australia/Sydney"

(lldb) po [NSTimeZone localTimeZone] (id) $2 = 0x0ab3bb10 Local Time Zone (Australia/Sydney (GMT+10:00) offset 36000)

"f" is an NSDateFormatter created just with alloc - init. As you can see the two time zones are exactly the same, stored at the same address.

Answer 2

It will take a localTimeZone by default.