Is my Contact's birthday in next 10 days

Question

I am trying to calculate whether any of my Address Book's contacts have a birthday in the next 10 days. There's plenty of code on line to compare dates, but I only want to compare day and month. For example, if a contact was born 05/01/1960 (and assuming today is 04/24/2011), then I only want to calculate that there are only six days till their birthday. Help appreciated.

Answer 1

Change the birthday to this year (or next year if the birthday was already in this year) and calculate with NSDateComponents and NSCalendar.

Looks a bit complicated, but you could do it like this:

NSDate *birthDay = ... // [calendar dateFromComponents:myBirthDay];

NSCalendar *calendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];

NSDateComponents *thisYearComponents = [calendar components:NSYearCalendarUnit fromDate:[NSDate date]];
NSDateComponents *birthDayComponents = [calendar components:NSMonthCalendarUnit|NSDayCalendarUnit fromDate:birthDay];
[birthDayComponents setYear:[thisYearComponents year]];

NSDate *birthDayThisYear = [calendar dateFromComponents:birthDayComponents];

NSDateComponents *difference = [calendar components:NSDayCalendarUnit fromDate:[NSDate date] toDate:birthDayThisYear options:0];
if ([difference day] < 0) {
    // this years birthday is already over. calculate distance to next years birthday
    [birthDayComponents setYear:[thisYearComponents year]+1];
    birthDayThisYear = [calendar dateFromComponents:birthDayComponents];
    difference = [calendar components:NSDayCalendarUnit fromDate:[NSDate date] toDate:birthDayThisYear options:0];
}


NSLog(@"%i days until birthday", [difference day]);