Baconbeastnz Baconbeastnz - 2 years ago 397
iOS Question

Objective-C, How can I get the current date in UTC timezone?

I am trying:

NSDate *currentDateInLocal = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:SS.SSS'Z'"];
NSString *currentLocalDateAsStr = [dateFormatter stringFromDate:currentDateInLocal];

NSDateFormatter * dateFormatter2 = [[NSDateFormatter alloc] init];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
[dateFormatter2 setTimeZone:timeZone];
[dateFormatter2 setDateFormat:@"yyyy-MM-dd'T'HH:mm:SS.SSS'Z'"];
NSDate *currentDateInUTC = [dateFormatter2 dateFromString:currentLocalDateAsStr];

but It's still does not represent the current UTC time, how can I achieve this?


Answer Source
NSDate *currentDate = [[NSDate alloc] init];

Now it is in UTC, (at least after using the method below)
To store this time as UTC (since refernce date 1970) use

double secsUtc1970 = [[NSDate date]timeIntervalSince1970];

Set Date formatter to output local time:

NSTimeZone *timeZone = [NSTimeZone defaultTimeZone];
// or Timezone with specific name like
// [NSTimeZone timeZoneWithName:@"Europe/Riga"] (see link below)
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setTimeZone:timeZone];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"];
NSString *localDateString = [dateFormatter stringFromDate:currentDate];

Available NSTimeZone names

A NSDate object always uses UTC as time reference, but the string representation of a date is not neccessarily based on UTC timezone.

Please note that UTC is not (only) a timeZone, It is a system how time on earth is measured, how it is coordinated (The C in UTC stands for coordinated).
The NSDate is related to a reference Date of midnight 1.1.1970 UTC, altough slightly wrongly described by Apple as 1.1.1970 GMT.

In the original question the last word timeZone is not perfect.

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