NSDateFormatter returns unexpected String from date

Question

I am using below code to create date string from Date

NSDate *localDate = [[[NSDate alloc] init] autorelease];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
[dateFormatter setTimeZone:timeZone];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss.S'Z'"];
NSString *dateString = [dateFormatter stringFromDate:localDate];

And I am expecting a result like "2016-01-06T01:14:18.8Z", it works as expected in most of the iPhones but in some phone above code generate date in different format like, "2016-01-06T12:59:17.6 a.m.Z".

Anybody knows what would be the root cause of this behaviour