Cocoa-Touch: How do I see if two NSDates are in the same day?

Question

I need to know if two NSDate instances are both from the same day.

Is there an easier/better way to do it than getting the NSDateComponents and comparing day/month/year?

Answer 1

NSDateComponents sounds like the best bet to me. Another tactic to try is toll-free-bridging it to a CFDate, then using CFDateGetAbsoluteTime and doing a subtraction to get the amount of time between the two dates. You'll have to do some additional math to figure out if the time difference lands the dates on the same day, however.

Answer 2

I just use a date formatter:

NSDateFormatter *dateComparisonFormatter = [[[NSDateFormatter alloc] init] autorelease];
[dateComparisonFormatter setDateFormat:@"yyyy-MM-dd"];

if( [[dateComparisonFormatter stringFromDate:firstDate] isEqualToString:[dateComparisonFormatter stringFromDate:secondDate]] ) {
    …
}

HTH.

Answer 3

I use NSDateComponents to strip out the time aspect and then compare. Something like:

if ([[self beginningOfDay:date1] isEqualToDate:[self beginningOfDay:date2]]) 
{
...
}

- (NSDate *)beginningOfDay:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
    NSDateComponents *comp = [calendar components:unitFlags fromDate:date];

    return [calendar dateFromComponents:comp];
}

Answer 4

NSDateComponents is my preference. How about something like this:

- (BOOL)isSameDay:(NSDate*)date1 (NSDate*)date2 {
    NSCalendar* calendar = [NSCalendar currentCalendar];

    unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
    NSDateComponents* comp1 = [calendar components:unitFlags fromDate:date1];
    NSDateComponents* comp2 = [calendar components:unitFlags fromDate:date2];

    return [comp1 day]   == [comp2 day] &&
           [comp1 month] == [comp2 month] &&
           [comp1 year]  == [comp2 year];
}