NSDate for "beginning of next hour"

Question

I'd like to make a countdown to the next full hour. It's pretty easy to countdown to a specific time, like:

NSDate *midnight = [NSDate dateWithNaturalLanguageString:@"midnight tomorrow"];

how do I define an NSDate for "the beginning of every hour"?

Thanks!

EDIT: This is what I have currently. Having trouble integrating the solutions in to my code. Any help would be greatly appreciated. :)

-(void)updateLabel {
NSDate *now = [NSDate date];

NSDate *midnight = [NSDate dateWithNaturalLanguageString:@"midnight tomorrow"]; 

//num of seconds between mid and now
NSTimeInterval timeInt = [midnight timeIntervalSinceDate:now];
int hour = (int) timeInt/3600;
int min = ((int) timeInt % 3600) / 60;
int sec = (int) timeInt % 60;
countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hour, min,sec];
}

score 17 · Accepted Answer · edited Feb 22 '10 at 07:43

17

As +dateWithNaturalLanguageString is available on MacOS SDK only and your're targeting iPhone you'll need to make a method of your own. I think NSCalendar class can help you:

- (NSDate*) nextHourDate:(NSDate*)inDate{
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *comps = [calendar components: NSEraCalendarUnit|NSYearCalendarUnit| NSMonthCalendarUnit|NSDayCalendarUnit|NSHourCalendarUnit fromDate: inDate];
    [comps setHour: [comps hour]+1]; // Here you may also need to check if it's the last hour of the day
    return [calendar dateFromComponents:comps];
}

I have not checked this code but it (at least this approach) must work.

edited Feb 22 '10 at 07:43

Chuck

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answered Feb 22 '10 at 07:34

Vladimir

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The code given will currently work (even if the next hour is midnight), but I think you should technically use NSCalendar's `dateByAddingComponents:toDate:` rather than manually adding the components. NSCalendar is the right answer, though. – Chuck Feb 22 '10 at 07:42
1

Yes dateByAddingComponents:toDate looks more appropriate, but you still need to reset minute and second components to 0 somehow? – Vladimir Feb 22 '10 at 07:50
What doesn't work exactly? I've just run this code - it works ok for me (still don't know if it will work in case next hour is midnight) – Vladimir Feb 22 '10 at 08:08
hi vladimir.. I've added some details to my original question. Thansk! – dot Feb 22 '10 at 08:47
replace dateWithNaturalLanguageString call with call to nextHourDate ? – Vladimir Feb 22 '10 at 08:58

Dulgan · Answer 2 · 2017-07-31T06:54:42.957

Using DateComponents and Date, you get it by adding a negative amount of minutes and one hour to the given date.

Swift3 (as an extension):

extension Date {
    public var nextHour: Date {
        let calendar = Calendar.current
        let minutes = calendar.component(.minute, from: self)
        let components = DateComponents(hour: 1, minute: -minutes)
        return calendar.date(byAdding: components, to: self) ?? self
    }
}

Use it with let nextHourDate = myDate.nextHour

See Apple Date and Time Programming Guide for reference.

===========================================================================

ObjectiveC (as a static method):

+ (NSDate *)nextHourDate:(NSDate *)date{
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *components = [calendar components:NSMinuteCalendarUnit|NSHourCalendarUnit fromDate:date];
    components.minute = -components.minute;
    components.hour = 1;
    return [calendar dateByAddingComponents:components toDate:date options:0];
}

And call it with :

[YourClass nextHourDate:yourDate];

Should be just components.hour =1; as we add the hours, we don't replace them. — blackjack75, May 30 '17 at 20:15
Swift code should have negative minutes, same as Obj-C does. — Ondrej Hanak, Jul 28 '17 at 13:19

pronebird · Answer 3 · 2014-05-06T18:17:42.187

6

The simplest way probably to manipulate timestamp, round it to the beginning of current hour and add 1 hour

- (NSDate*)nextHourDateForDate:(NSDate*)date {
    NSTimeInterval timestamp = [date timeIntervalSince1970];
    NSTimeInterval current = timestamp - fmod(timestamp, 3600);
    NSTimeInterval next = current + 3600;

    return [NSDate dateWithTimeIntervalSince1970:next];
}

edited May 06 '14 at 18:17

answered Nov 02 '13 at 23:18

pronebird

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Nice, also works for next half-hour or next ten minutes, just change the 3600 to next any seconds. – Rob van den Berg Nov 21 '14 at 09:10

score 3 · Answer 4 · answered Feb 23 '10 at 02:01

3

You might want to check this out. Erica Sadun posted some extensions to NSDate.

http://github.com/erica/NSDate-Extensions

answered Feb 23 '10 at 02:01

xyzzycoder

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Very useful extension, but it doesn't help with the OP's question. – Toland Hon Jun 24 '15 at 23:28

score 1 · Answer 5 · answered Sep 07 '12 at 11:31

I think this would work (note: very briefly tested)

NSDateFormatter *currentSecondFormatter = [[NSDateFormatter alloc] init];
[currentSecondFormatter setDateFormat:@"ss"];
NSDateFormatter *currentMinuteFormatter = [[NSDateFormatter alloc] init];
[currentMinuteFormatter setDateFormat:@"mm"];

// get next hour from now
int timeUntilNextHour = ( (60 - [[currentMinuteFormatter stringFromDate:[NSDate date]] integerValue]) * 60) -  [[currentSecondFormatter stringFromDate:[NSDate date]] integerValue];

Please check your code before submitting it. "I think ..." is not good. — Johan Karlsson, Sep 27 '12 at 13:26

score 0 · Answer 6 · answered Feb 13 '15 at 14:23

Maybe this can be helpful

@implementation NSDate (DB_Extension)

- (NSTimeInterval)db_secondsForNextHour {

NSDateFormatter *minutesFormatter = [[NSDateFormatter alloc] init];
[minutesFormatter setDateFormat:@"mm"];

NSDateFormatter *secondsFormatter = [[NSDateFormatter alloc] init];
[secondsFormatter setDateFormat:@"ss.SSS"];

NSTimeInterval secondsForNextHour = (60.0 - [[minutesFormatter stringFromDate:self] doubleValue])*60 - [[secondsFormatter stringFromDate:self] doubleValue];

return secondsForNextHour;

}

NSDate for "beginning of next hour"

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