How to calculate the age based on NSDate

Many of these answers don't properly account for leap years and such, best is to use Apple's methods instead of dividing by constants.

Swift

let birthday: NSDate = ...let now = Date()let ageComponents = calendar.dateComponents([.year], from: birthday, to: now)let age = ageComponents.year

Objective-C

NSDate* birthday = ...;NSDate* now = [NSDate date];NSDateComponents* ageComponents = [[NSCalendar currentCalendar]                                    components:NSCalendarUnitYear                                    fromDate:birthday                                   toDate:now                                   options:0];NSInteger age = [ageComponents year];

I think this is cleaner and more accurate than any of the other answers here.

Edit

Increase accuracy by setting both birthday and now to noon. Here is one way to do that with a Date extension (in Swift)...

/// Returns a new date identical to the receiver except set to precisely noon./// Example: let now = Date().atNoon()func atNoon() -> Date {    var components = (Calendar.current as NSCalendar).components([.day, .month, .year, .era, .calendar, .timeZone], from: self)    components.hour = 12    components.minute = 0    components.second = 0    components.nanosecond = 0    return Calendar.current.date(from: components)!}

Here's how you can calculate your actual age based on your birth date in years and days:

NSString *birthDate = @"03/31/1990";    NSDate *todayDate = [NSDate date];NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];[dateFormatter setDateFormat:@"MM/dd/yyyy"];int time = [todayDate timeIntervalSinceDate:[dateFormatter dateFromString:birthDate]];int allDays = (((time/60)/60)/24);int days = allDays%365;int years = (allDays-days)/365;NSLog(@"You live since %i years and %i days",years,days);

It returns the years and the exact days. And if you need you can change the NSDateFormatter and much more.

This is the code I got from this link.. it works great.. Out put will be like "5 years 6 months" and all usecases are covered in it.

- (NSString *)age:(NSDate *)dateOfBirth {   NSInteger years;   NSInteger months;   NSInteger days;   NSCalendar *calendar = [NSCalendar currentCalendar];    unsigned unitFlags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;   NSDateComponents *dateComponentsNow = [calendar components:unitFlags fromDate:[NSDate date]];   NSDateComponents *dateComponentsBirth = [calendar components:unitFlags fromDate:dateOfBirth];   if (([dateComponentsNow month] < [dateComponentsBirth month]) ||(([dateComponentsNow month] == [dateComponentsBirth month]) && ([dateComponentsNow day] < [dateComponentsBirth day]))) {   years = [dateComponentsNow year] - [dateComponentsBirth year] - 1;} else {   years = [dateComponentsNow year] - [dateComponentsBirth year];}if ([dateComponentsNow year] == [dateComponentsBirth year]) {   months = [dateComponentsNow month] - [dateComponentsBirth month];} else if ([dateComponentsNow year] > [dateComponentsBirth year] && [dateComponentsNow month] > [dateComponentsBirth month]) {   months = [dateComponentsNow month] - [dateComponentsBirth month];} else if ([dateComponentsNow year] > [dateComponentsBirth year] && [dateComponentsNow month] < [dateComponentsBirth month]) {   months = [dateComponentsNow month] - [dateComponentsBirth month] + 12;} else {   months = [dateComponentsNow month] - [dateComponentsBirth month];}if ([dateComponentsNow year] == [dateComponentsBirth year] && [dateComponentsNow month] == [dateComponentsBirth month]) {   days = [dateComponentsNow day] - [dateComponentsBirth day];}if (years == 0 && months == 0) {   if (days == 1) {      return [NSString stringWithFormat:@"%d day", days];   } else {      return [NSString stringWithFormat:@"%d days", days];   }} else if (years == 0) {   if (months == 1) {      return [NSString stringWithFormat:@"%d month", months];   } else {      return [NSString stringWithFormat:@"%d months", months];   }} else if ((years != 0) && (months == 0)) {   if (years == 1) {       return [NSString stringWithFormat:@"%d year", years];   } else {       return [NSString stringWithFormat:@"%d years", years];   }} else {  if ((years == 1) && (months == 1)) {      return [NSString stringWithFormat:@"%d year and %d month", years, months];  } else if (years == 1) {      return [NSString stringWithFormat:@"%d year and %d months", years, months];  } else if (months == 1) {      return [NSString stringWithFormat:@"%d years and %d month", years, months];  } else {      return [NSString stringWithFormat:@"%d years and %d months", years, months];  }}}

If you want age as int try the following answer.. which I got from following link

- (NSInteger)age:(NSDate *)dateOfBirth {  NSCalendar *calendar = [NSCalendar currentCalendar];  unsigned unitFlags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;  NSDateComponents *dateComponentsNow = [calendar components:unitFlags fromDate:[NSDate date]];  NSDateComponents *dateComponentsBirth = [calendar components:unitFlags fromDate:dateOfBirth];  if (([dateComponentsNow month] < [dateComponentsBirth month]) ||      (([dateComponentsNow month] == [dateComponentsBirth month]) && ([dateComponentsNow day] < [dateComponentsBirth day]))) {    return [dateComponentsNow year] - [dateComponentsBirth year] - 1;  } else {    return [dateComponentsNow year] - [dateComponentsBirth year];  }}

Hope this helps some one..