Ensure AM / PM (Period) does not appear in NSDateFormat stringFromDate - ios

Question

The Unicode Date Format Patterns guide (here) state that appending an 'a' to the format will get the period (AM or PM for instance), e.g.,
[formatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss a"];
However I wish to ensure that the period information does not appear but I cannot find a format string to do that. The format string I am using is as follows:
[formatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss"];
unfortunately, when I use stringFromDate I get the following:
2013-01-09T11:11:00 AM
I dont wish to simply strip AM or PM from the resultant string because the period syntax may be different in differing Calendars etc, I just want to stop the period information appearing.
----8<------
Consider the following code
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setLocale:[NSLocale currentLocale]];
[formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
[formatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss"];
NSString *stringDate = [formatter stringFromDate:[NSDate date]];
self.labelOutput.text = stringDate;
[formatter release];
This code will produce a string in the format I want - however I cannot use it for memory management reasons. The app I am working on is plagued by NSDateFormatter memory leaks. So we use a singleton class to provide a set number NSDateFormatters to the app which are never released and therefore we minimise how much memory is being leaked. Unfortunately these static NSDateFormatters are appending AM / PM even when I apply a date format string thus:
NSDateFormatter *formatter = [MyDateFormatter dateFormat:kFormatDateMediumStyleTimeShortStyle];
[formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
[formatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss"];

Answer 1

According to date formatter different output on different devices running same iOS version, set the local of your NSDateFormatter to en_US_POSIX will fix this.
Additional to set Local you may wish avoid problems with time zone setting it like:
[formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];

Answer 2

It actually depends on user's settings.
Please see Fixed Formats part of Data Formatting Guide. Note this sentence:
In iOS, the user can override the default AM/PM versus 24-hour time
setting. This may cause NSDateFormatter to rewrite the format string
you set.
And at the end of the paragraph:
The representation of the time may be 13:00. In iOS, however, if the
user has switched 24-Hour Time to Off, the time may be 1:00 pm.

Answer 3

You need to use POSIX here a sample code
NSDateFormatter *rfc3339DateFormatter = [[NSDateFormatter alloc] init];
NSLocale *enUSPOSIXLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
[rfc3339DateFormatter setLocale:enUSPOSIXLocale];
[rfc3339DateFormatter setDateFormat:#"yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"];
[rfc3339DateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
// Convert the RFC 3339 date time string to an NSDate.
NSDate *date = [rfc3339DateFormatter dateFromString:rfc3339DateTimeString];

Answer 4

One option is to create your own NSFormatter. I did that on my code when I couldn't get the formatter in Xcode's Interface Builder to do what I wanted. Granted, I was only looking for hours, minutes, and seconds and not the full date.
As for the memory leaks: if you can, use ARC. If you can't, use Xcode's Static Analyzer to try and track down improper retain counts.

Answer 5

Here is the answer I have settled on. It's a bit simplistic but it does the job.
#interface NSDateFormatter (Utils)
- (NSString *)stringWithNoPeriodInformationFromDate:(NSDate*)date;
#end
#implementation NSDateFormatter (Utils)
- (NSString *)stringWithNoPeriodInformationFromDate:(NSDate*)date
{
NSString *stringWithPotentialPeriodInformation = [self stringFromDate:date];
NSString *stringWithNoAMInformation = [stringWithPotentialPeriodInformation stringByReplacingOccurrencesOfString:[self AMSymbol] withString:#""];
NSString *stringWithNoPeriodInformation = [stringWithNoAMInformation stringByReplacingOccurrencesOfString:[self PMSymbol] withString:#""];
return stringWithNoPeriodInformation;
}
#end