gistfile1.m

// Get current date in ISO 8601 string
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSLocale *enUSPOSIXLocale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
[dateFormatter setLocale:enUSPOSIXLocale];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ssZ"];

NSDate *now = [NSDate date];
NSString *endedAt = [dateFormatter stringFromDate:now];
self.workoutSessionManager.workoutSession.endedAt = endedAt