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.

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

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.

edited Jun 20 '20 at 09:12

Community

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answered Sep 27 '12 at 03:55

Ben Trengrove

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Yes, I added it to the answer above. They are different. – Ben Trengrove Sep 27 '12 at 04:13
This answer has some pretty good explanation on the timezone types. http://stackoverflow.com/questions/1526990/nstimezone-what-is-the-difference-between-localtimezone-and-systemtimezone – Ben Trengrove Sep 27 '12 at 04:14
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It is stated in the [Data Formatting Guide](http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/DataFormatting/Articles/dfDateFormatting10_4.html#//apple_ref/doc/uid/TP40002369-SW1), though not quite explicitly: «In all cases, you should consider that formatters default to using the user’s locale (`currentLocale`) superimposed with the user’s preference settings.» The locale includes a time zone. – jscs Sep 27 '12 at 17:30

score 0 · Answer 2 · edited Sep 27 '12 at 07:02

0

It will take a localTimeZone by default.

edited Sep 27 '12 at 07:02

Gerstmann

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answered Sep 27 '12 at 04:20

Kasaname

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

2 Answers2