Number of days between two NSDates [duplicate]

Answer 1

@Brian

Brian's answer while good, only calculates difference in days in terms of 24h chunks, but not calendar day differences. For example 23:59 on Dec 24th is only 1 minute away from Christmas Day, for the purpose of many application that is considered one day still. Brian's daysBetween function would return 0.

Borrowing from Brian's original implementation and beginning/end of day, I use the following in my program: (NSDate beginning of day and end of day)

- (NSDate *)beginningOfDay:(NSDate *)date
{
    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDateComponents *components = [cal components:( NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit ) fromDate:date];
    [components setHour:0];
    [components setMinute:0];
    [components setSecond:0];
    return [cal dateFromComponents:components];
}

- (NSDate *)endOfDay:(NSDate *)date
{
    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDateComponents *components = [cal components:( NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit ) fromDate:date];
    [components setHour:23];
    [components setMinute:59];
    [components setSecond:59];
    return [cal dateFromComponents:components];
}

- (int)daysBetween:(NSDate *)date1 and:(NSDate *)date2 {
    NSDate *beginningOfDate1 = [self beginningOfDay:date1];
    NSDate *endOfDate1 = [self endOfDay:date1];
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *beginningDayDiff = [calendar components:NSDayCalendarUnit fromDate:beginningOfDate1 toDate:date2 options:0];
    NSDateComponents *endDayDiff = [calendar components:NSDayCalendarUnit fromDate:endOfDate1 toDate:date2 options:0];
    if (beginningDayDiff.day > 0)
        return beginningDayDiff.day;
    else if (endDayDiff.day < 0)
        return endDayDiff.day;
    else {
        return 0;
    }
}