CODEWITHSUNDEEP
iphoneobjective-ciosnsdatenstimeinterval
Sharon Watinsan
Sharon Watinsan

Reputation: 9850

Calculate time difference between 2 time intervals - Logic issue

I have a String with the time as follows;

NSString *time = "06.45 pm";

I need to assume that this time is on today's date and then get the current System time, and calculate the time difference between the two.

How can i do this ?

Note: The above time doesn't specify a date, (Only the time is given)

Upvotes: 1

Views: 7516

Answers (2)

lnafziger
lnafziger

Reputation: 25740

Make sure that when you do this that you are using calendar operations so that it takes into account time changes (daylight savings time, leap seconds, etc.):

NSString    *time  = @"06.45 pm";
NSCalendar  *cal   = [NSCalendar currentCalendar];
NSDate      *today = [NSDate date];

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"hh.mm a"];

// Convert time to a NSDate and break it down into hours, minutes, and seconds:
NSDate           *timeAsDate = [formatter dateFromString:time];
NSDateComponents *timeComps  = [cal components:NSHourCalendarUnit |
                                               NSMinuteCalendarUnit |
                                               NSSecondCalendarUnit
                                      fromDate:timeAsDate];

// Take today's date and add "time" to it:
NSDateComponents *comps  = [cal components:NSYearCalendarUnit |
                                           NSMonthCalendarUnit |
                                           NSDayCalendarUnit
                                  fromDate:today];
comps.hour               = timeComps.hour;
comps.minute             = timeComps.minute;
comps.second             = timeComps.second;
NSDate *timeOnTodaysDate = [cal dateFromComponents:comps];

// Now calculate the difference:
NSTimeInterval difference = [today timeIntervalSinceDate:timeOnTodaysDate];

Upvotes: 2

Joey
Joey

Reputation: 2968

NSString *time = @"06.45 pm";

NSDate *date1;
NSDate *date2;
{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"hh.mm a"];
    date1 = [formatter dateFromString:time];
    date2 = [formatter dateFromString:[formatter stringFromDate:[NSDate date]]];
    [formatter release];
}
NSTimeInterval interval = [date1 timeIntervalSinceDate: date2];//[date1 timeIntervalSince1970] - [date2 timeIntervalSince1970];
int hour = interval / 3600;
int minute = (int)interval % 3600 / 60;

NSLog(@"%@ %dh %dm", interval<0?@"-":@"+", ABS(hour), ABS(minute));

Upvotes: 3

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