Step1: Create a function named “convertToUTC“, which will accept a string parameter and that is the date we want to convert into UTC timezone and returns the converted date in UTC timezone as a string. Step2: We will create a “DateFormatter” that has a date format “dd-MM-yyyy hh:mm a“.
The ToLocalTime method converts a DateTime value from UTC to local time. To convert the time in any designated time zone to local time, use the TimeZoneInfo. ConvertTime method. The value returned by the conversion is a DateTime whose Kind property always returns Local.
UTC time in ISO-8601 is 12:20:18Z. Note that the Z letter without a space.
NSTimeInterval seconds; // assume this exists
NSDate* ts_utc = [NSDate dateWithTimeIntervalSince1970:seconds];
NSDateFormatter* df_utc = [[[NSDateFormatter alloc] init] autorelease];
[df_utc setTimeZone:[NSTimeZone timeZoneWithName:@"UTC"]];
[df_utc setDateFormat:@"yyyy.MM.dd G 'at' HH:mm:ss zzz"];
NSDateFormatter* df_local = [[[NSDateFormatter alloc] init] autorelease];
[df_local setTimeZone:[NSTimeZone timeZoneWithName:@"EST"]];
[df_local setDateFormat:@"yyyy.MM.dd G 'at' HH:mm:ss zzz"];
NSString* ts_utc_string = [df_utc stringFromDate:ts_utc];
NSString* ts_local_string = [df_local stringFromDate:ts_utc];
// you can also use NSDateFormatter dateFromString to go the opposite way
Table of formatting string parameters:
https://waracle.com/iphone-nsdateformatter-date-formatting-table/
If performance is a priority, you may want to consider using strftime
https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/strftime.3.html
EDIT When i wrote this I didn't know I should use a dateformatter which is probably a better approach, so check out slf
's answer too.
I have a webservice that returns dates in UTC. I use toLocalTime
to convert it to local time and toGlobalTime
to convert back if needed.
This is where I got my answer from:
https://agilewarrior.wordpress.com/2012/06/27/how-to-convert-nsdate-to-different-time-zones/
@implementation NSDate(Utils)
-(NSDate *) toLocalTime
{
NSTimeZone *tz = [NSTimeZone defaultTimeZone];
NSInteger seconds = [tz secondsFromGMTForDate: self];
return [NSDate dateWithTimeInterval: seconds sinceDate: self];
}
-(NSDate *) toGlobalTime
{
NSTimeZone *tz = [NSTimeZone defaultTimeZone];
NSInteger seconds = -[tz secondsFromGMTForDate: self];
return [NSDate dateWithTimeInterval: seconds sinceDate: self];
}
@end
The easiest method I've found is this:
NSDate *someDateInUTC = …;
NSTimeInterval timeZoneSeconds = [[NSTimeZone localTimeZone] secondsFromGMT];
NSDate *dateInLocalTimezone = [someDateInUTC dateByAddingTimeInterval:timeZoneSeconds];
Swift 3+: UTC to Local and Local to UTC
extension Date {
// Convert UTC (or GMT) to local time
func toLocalTime() -> Date {
let timezone = TimeZone.current
let seconds = TimeInterval(timezone.secondsFromGMT(for: self))
return Date(timeInterval: seconds, since: self)
}
// Convert local time to UTC (or GMT)
func toGlobalTime() -> Date {
let timezone = TimeZone.current
let seconds = -TimeInterval(timezone.secondsFromGMT(for: self))
return Date(timeInterval: seconds, since: self)
}
}
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