How can I calculate the difference between two dates?
Solution 1:
NSDate *date1 = [NSDate dateWithString:@"2010-01-01 00:00:00 +0000"];
NSDate *date2 = [NSDate dateWithString:@"2010-02-03 00:00:00 +0000"];
NSTimeInterval secondsBetween = [date2 timeIntervalSinceDate:date1];
int numberOfDays = secondsBetween / 86400;
NSLog(@"There are %d days in between the two dates.", numberOfDays);
EDIT:
Remember, NSDate
objects represent exact moments of time, they do not have any associated time-zone information. When you convert a string to a date using e.g. an NSDateFormatter
, the NSDateFormatter
converts the time from the configured timezone. Therefore, the number of seconds between two NSDate
objects will always be time-zone-agnostic.
Furthermore, this documentation specifies that Cocoa's implementation of time does not account for leap seconds, so if you require such accuracy, you will need to roll your own implementation.
Solution 2:
You may want to use something like this:
NSDateComponents *components;
NSInteger days;
components = [[NSCalendar currentCalendar] components: NSDayCalendarUnit
fromDate: startDate toDate: endDate options: 0];
days = [components day];
I believe this method accounts for situations such as dates that span a change in daylight savings.
Solution 3:
NSTimeInterval diff = [date2 timeIntervalSinceDate:date1]; // in seconds
where date1
and date2
are NSDate
's.
Also, note the definition of NSTimeInterval
:
typedef double NSTimeInterval;