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Asked: 2026-05-28T19:25:48+00:00

I’m having an issue converting minutes since midnight to a correct time. It works

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I’m having an issue converting minutes since midnight to a correct time. It works fine until i reach noon. At which point the time becomes 0:45AM and anything after noon is blank. Am I missing something in my format?

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
    [dateFormatter setDateFormat:@"h:m"];
    NSLog(@"Minutes %i",minutes);
    NSString *time = [NSString stringWithFormat:@"%i:%i", (minutes / 60), (minutes % 60)];
    NSLog(@"time: %@",time);
    NSDate *formatTime = [dateFormatter dateFromString:time];
    NSLog(@"formatTime %@",formatTime);
    dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en-US"];
    [dateFormatter setDateFormat:@"H:mma"];
    NSString *newTime = [dateFormatter stringFromDate:formatTime];
    NSLog(@"NewTime: %@",newTime);
    dateFormatter = nil;

Log

2012-01-25 15:12:23.194 MyApp[43875:f803] Minutes 480
2012-01-25 15:12:23.194 MyApp[43875:f803] time: 8:0
2012-01-25 15:12:23.195 MyApp[43875:f803] formatTime 1970-01-01 15:00:00 +0000
2012-01-25 15:12:23.196 MyApp[43875:f803] NewTime: 8:00AM
2012-01-25 15:12:23.197 MyApp[43875:f803] Minutes 495
2012-01-25 15:12:23.197 MyApp[43875:f803] time: 8:15
2012-01-25 15:12:23.198 MyApp[43875:f803] formatTime 1970-01-01 15:15:00 +0000
2012-01-25 15:12:23.199 MyApp[43875:f803] NewTime: 8:15AM
2012-01-25 15:12:23.200 MyApp[43875:f803] Minutes 765
2012-01-25 15:12:23.200 MyApp[43875:f803] time: 12:45
2012-01-25 15:12:23.201 MyApp[43875:f803] formatTime 1970-01-01 07:45:00 +0000
2012-01-25 15:12:23.201 MyApp[43875:f803] NewTime: 0:45AM
2012-01-25 15:12:23.203 MyApp[43875:f803] Minutes 480
2012-01-25 15:12:23.203 MyApp[43875:f803] time: 8:0
2012-01-25 15:12:23.204 MyApp[43875:f803] formatTime 1970-01-01 15:00:00 +0000
2012-01-25 15:12:23.204 MyApp[43875:f803] NewTime: 8:00AM
2012-01-25 15:12:23.205 MyApp[43875:f803] Minutes 495
2012-01-25 15:12:23.206 MyApp[43875:f803] time: 8:15
2012-01-25 15:12:23.206 MyApp[43875:f803] formatTime 1970-01-01 15:15:00 +0000
2012-01-25 15:12:23.207 MyApp[43875:f803] NewTime: 8:15AM
2012-01-25 15:12:23.208 MyApp[43875:f803] Minutes 555
2012-01-25 15:12:23.209 MyApp[43875:f803] time: 9:15
2012-01-25 15:12:23.209 MyApp[43875:f803] formatTime 1970-01-01 16:15:00 +0000
2012-01-25 15:12:23.210 MyApp[43875:f803] NewTime: 9:15AM
2012-01-25 15:12:23.211 MyApp[43875:f803] Minutes 630
2012-01-25 15:12:23.211 MyApp[43875:f803] time: 10:30
2012-01-25 15:12:23.212 MyApp[43875:f803] formatTime 1970-01-01 17:30:00 +0000
2012-01-25 15:12:23.212 MyApp[43875:f803] NewTime: 10:30AM
2012-01-25 15:12:23.214 MyApp[43875:f803] Minutes 690
2012-01-25 15:12:23.214 MyApp[43875:f803] time: 11:30
2012-01-25 15:12:23.215 MyApp[43875:f803] formatTime 1970-01-01 18:30:00 +0000
2012-01-25 15:12:23.215 MyApp[43875:f803] NewTime: 11:30AM
2012-01-25 15:12:23.217 MyApp[43875:f803] Minutes 765
2012-01-25 15:12:23.217 MyApp[43875:f803] time: 12:45
2012-01-25 15:12:23.217 MyApp[43875:f803] formatTime 1970-01-01 07:45:00 +0000
2012-01-25 15:12:23.218 MyApp[43875:f803] NewTime: 0:45AM
2012-01-25 15:12:32.506 MyApp[43875:f803] Minutes 840
2012-01-25 15:12:32.507 MyApp[43875:f803] time: 14:0
2012-01-25 15:12:32.507 MyApp[43875:f803] formatTime (null)
2012-01-25 15:12:32.508 MyApp[43875:f803] NewTime: (null)

EDIT:
I am using Munid’s Edit 2 below and it works well except it seems to be subtracting 7 hours from newDate when I run it through the dateFormatter

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
    //dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en-US"];
    [dateFormatter setDateFormat:@"hh:mm a"];
    NSDate *midnight = [NSDate dateWithTimeIntervalSince1970:0];
    NSLog(@"midnight %@",midnight);
    NSDate *newDate = [midnight dateByAddingTimeInterval:minutes*60];
    NSLog(@"new date %@", newDate);
    //[dateFormatter setDateFormat:@"hh:mma"];
    NSString *newTime = [dateFormatter stringFromDate:newDate];
    NSLog(@"Time: %@", newTime);
    dateFormatter = nil;

will log

2012-01-25 16:15:03.418 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.418 MyApp[44721:f803] new date 1970-01-01 08:00:00 +0000
2012-01-25 16:15:03.419 MyApp[44721:f803] Time: 01:00 AM
2012-01-25 16:15:03.420 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.420 MyApp[44721:f803] new date 1970-01-01 08:15:00 +0000
2012-01-25 16:15:03.420 MyApp[44721:f803] Time: 01:15 AM
2012-01-25 16:15:03.421 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.422 MyApp[44721:f803] new date 1970-01-01 12:45:00 +0000
2012-01-25 16:15:03.422 MyApp[44721:f803] Time: 05:45 AM
2012-01-25 16:15:03.423 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.424 MyApp[44721:f803] new date 1970-01-01 08:00:00 +0000
2012-01-25 16:15:03.424 MyApp[44721:f803] Time: 01:00 AM
2012-01-25 16:15:03.425 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.425 MyApp[44721:f803] new date 1970-01-01 08:15:00 +0000
2012-01-25 16:15:03.426 MyApp[44721:f803] Time: 01:15 AM
2012-01-25 16:15:03.427 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.427 MyApp[44721:f803] new date 1970-01-01 09:15:00 +0000
2012-01-25 16:15:03.427 MyApp[44721:f803] Time: 02:15 AM
2012-01-25 16:15:03.428 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.429 MyApp[44721:f803] new date 1970-01-01 09:30:00 +0000
2012-01-25 16:15:03.429 MyApp[44721:f803] Time: 02:30 AM
2012-01-25 16:15:03.430 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.431 MyApp[44721:f803] new date 1970-01-01 10:30:00 +0000
2012-01-25 16:15:03.431 MyApp[44721:f803] Time: 03:30 AM
2012-01-25 16:15:03.432 MyApp[44721:f803] midnight 1970-01-01 00:00:00 +0000
2012-01-25 16:15:03.432 MyApp[44721:f803] new date 1970-01-01 11:30:00 +0000
2012-01-25 16:15:03.433 MyApp[44721:f803] Time: 04:30 AM
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1 Answer

  1. Editorial Team

    First, maybe your method with format strings is a little bit too involved. Don’t forget, that the NSLog output also needs to be formatted, otherwise you will get a different locale and time zone, so these values are not reliable for checking if your logic is right.

    The simple solution is to use the fact that NSTimeInterval is in seconds. Thus:

    NSDate *midnight; // the date you want, at 0:00 am
NSDate *newDate = [midnight dateByAddingTimeInterval:minutes*60];

    EDIT:

    Also, I checked your code – you can fix it by changing the format strings. The problem was that the date formatter got confused with the minute having 1 or 2 digits. 

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
for (NSInteger minutes = 495; minutes < 1000; minutes +=60) {
    [dateFormatter setDateFormat:@"hh:mm"];
    NSLog(@"Minutes %2i",minutes);
    NSString *time = [NSString stringWithFormat:@"%2i:%2i", (minutes / 60), (minutes % 60)];
    NSLog(@"time: %@",time);
    NSDate *formatTime = [dateFormatter dateFromString:time];
    NSLog(@"formatTime %@",formatTime);
    dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en-US"];
    [dateFormatter setDateFormat:@"HH:mm a"];
    NSString *newTime = [dateFormatter stringFromDate:formatTime];
    NSLog(@"NewTime: %@",newTime);
}
dateFormatter = nil;

    EDIT2:

    Expanding on the code above as requested: 

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"hh:mm a"];
NSDate *midnight = [NSDate dateWithTimeIntervalSince1970:0];
for (NSInteger minutes = 495; minutes < 1000; minutes +=60) {
    NSDate *newDate = [midnight dateByAddingTimeInterval:minutes*60];
    NSLog(@"newDate: %@", [dateFormatter stringFromDate:newDate]);
}
dateFormatter = nil;
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