CODEWITHSUNDEEP
iphonensdate
g.revolution
g.revolution

Reputation: 12262

GMT time on iPhone

How do I get GMT time?

NSDate *c =[NSDate date];

gives system time, not GMT.

Upvotes: 8

Views: 17448

Answers (7)

Evan Schoenberg
Evan Schoenberg

Reputation: 943

If performing date calculations, these categories may be useful. Having converted your date to being 'normalized' (that is, having the same month, day, and year but at +1200 UTC), if you then perform subsequent calculations using an NSCalendar that is also set to UTC (+[NSCalendar normalizedCalendar]), it'll all work out.

@implementation NSDate (NormalizedAdditions)

+ (NSDate *)normalizedDateFromDateInCurrentCalendar:(NSDate *)inDate
{
    NSDateComponents *todayComponents = [[NSCalendar currentCalendar] components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)
                                                                        fromDate:inDate];
    [todayComponents setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
    [todayComponents setHour:12];

    return [[NSCalendar normalizedCalendar] dateFromComponents:todayComponents];
}

+ (NSDate *)normalizedDate
{
    return [self normalizedDateFromDateInCurrentCalendar:[NSDate date]];
}

@end

@implementation NSCalendar (NormalizedAdditions)

+ (NSCalendar *)normalizedCalendar
{
    static NSCalendar *gregorian = nil;
    if (!gregorian) {
        gregorian = [[NSCalendar alloc]
                     initWithCalendarIdentifier:NSGregorianCalendar];
        [gregorian setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];   
    }
    return gregorian;
}

@end

Upvotes: 4

Bill Wynne
Bill Wynne

Reputation: 53

+ (NSDate*) convertToGMT:(NSDate*)sourceDate
{
    NSTimeZone* currentTimeZone = [NSTimeZone localTimeZone];

    NSTimeInterval gmtInterval = [currentTimeZone secondsFromGMTForDate:sourceDate];

    NSDate* destinationDate = [[[NSDate alloc] initWithTimeInterval:gmtInterval sinceDate:sourceDate] autorelease];     
    return destinationDate;
}

Upvotes: 2

Chris
Chris

Reputation: 2747

This is a simpler version of Ramin's answer

+ (NSDate *) GMTNow
{ 
 NSDate *sourceDate = [NSDate date];
    NSTimeZone* currentTimeZone = [NSTimeZone localTimeZone];
    NSInteger currentGMTOffset = [currentTimeZone secondsFromGMT];

    [sourceDate addTimeInterval:currentGMTOffset];

    return sourceDate;
}

Upvotes: 9

Barry Hurley
Barry Hurley

Reputation: 577

If it's for display purposes you want to display it, use NSDateFormatter like so:

NSDate *myDate = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"GMT"]];

// Set date style:
[dateFormatter setDateStyle:NSDateFormatterShortStyle];
[dateFormatter setTimeStyle:NSDateFormatterShortStyle];

NSString *GMTDateString = [dateFormatter stringFromDate: myDate];

Upvotes: 8

Ramin
Ramin

Reputation: 13433

- (NSDate*) convertToUTC:(NSDate*)sourceDate
{
    NSTimeZone* currentTimeZone = [NSTimeZone localTimeZone];
    NSTimeZone* utcTimeZone = [NSTimeZone timeZoneWithAbbreviation:@"UTC"];

    NSInteger currentGMTOffset = [currentTimeZone secondsFromGMTForDate:sourceDate];
    NSInteger gmtOffset = [utcTimeZone secondsFromGMTForDate:sourceDate];
    NSTimeInterval gmtInterval = gmtOffset - currentGMTOffset;

    NSDate* destinationDate = [[[NSDate alloc] initWithTimeInterval:gmtInterval sinceDate:sourceDate] autorelease]; 
    return destinationDate;
}

Upvotes: -4

mahboudz
mahboudz

Reputation: 39376

See:

CFTimeZoneCreateWithTimeIntervalFromGMT secondsFromGMT

Date & Time Programming Guide

Upvotes: 0

olliej
olliej

Reputation: 36803

NSDate stores the time zone internally -- there are a few functions you can call and pass in a target timezone if you jsut want a string representation of the date, see apple's documentation

Upvotes: 0

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