iOS - Init NSDate with a stringDate without timezone calculations - ios

Question

I am getting a date time from web service which is in UTC format. Now i want to assign it to NSDate. Following is the code i have done
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
//[dateFormatter setTimeZone:[NSTimeZone localTimeZone]];
[dateFormatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss"];
NSDate *utcDate = [dateFormatter dateFromString:#"2015-08-18T23:00:00"];
but it is calculating its timezone calculations by default the result is 2015-08-19 03:00:00 +0000. How can i initialize NSDate with same date and Time. I want to perform timezone calculations later on

Answer 1

edit/update:
Xcode 11 • Swift 5.1:
let dateString = "2015-08-18T23:00:00"
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
formatter.calendar = Calendar(identifier: .iso8601)
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = TimeZone(secondsFromGMT: 0)
if let dateFromString = formatter.date(from: dateString) {
print(dateFromString) // "2015-08-18 23:00:00 +0000"
}

Answer 2

A default-allocated NSDateFormatter will use the current locale (the one that the user set up in Settings.app).
You have to explicitly set a suitable locale on the formatter:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
This locale uses the gregorian calendar on UTC without any DST adjustments.
Edit: LeoDabus points out that setting the locale does not change the timezone of the date formatter. This has to be done explicitly:
dateFormatter.timeZone = NSTimeZone(forSecondsFromGMT: 0)

Answer 3

NSString *dateStr =[NSString stringWithFormat:#"%#",[dict valueForKey:#"utc_datetime"]];
NSString* input = dateStr;
NSString* format = #"dd MMM yyyy - HH:mm:ss'";
// Set up an NSDateFormatter for UTC time zone
NSDateFormatter* formatterUtc = [[NSDateFormatter alloc] init];
[formatterUtc setDateFormat:format];
[formatterUtc setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
// Cast the input string to NSDate
NSDate* utcDate = [formatterUtc dateFromString:input];
// Set up an NSDateFormatter for the device's local time zone
NSDateFormatter* formatterLocal = [[NSDateFormatter alloc] init];
[formatterLocal setDateFormat:format];
[formatterLocal setTimeZone:[NSTimeZone localTimeZone]];
// Create local NSDate with time zone difference
NSDate* localDate = [formatterUtc dateFromString:[formatterLocal stringFromDate:utcDate]];
NSLog(#"utc: %#", utcDate);
NSLog(#"local: %#", localDate);
NSDateFormatter *format1q = [[NSDateFormatter alloc] init];
format1q.dateFormat = #"HH:mm";
NSString *StrDAte=[NSString stringWithFormat:#"%#",[format1q stringFromDate:utcDate]];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = #"HH:mm";
NSDate *date = [dateFormatter dateFromString:StrDAte];
date = [date dateByAddingTimeInterval:-60];
dateFormatter.dateFormat = #"hh:mm a";
NSString *pmamDateString = [dateFormatter stringFromDate:date];