Calculate age from an NSDate in Objective C – updated

Say that you have an NSDate and you want a NSString describing the age according to that date.

Here is a method that may be can help you:

- (NSString *)age:(NSDate *)dateOfBirth {

    NSInteger years;
    NSInteger months;
    NSInteger days;

    NSCalendar *calendar = [NSCalendar currentCalendar];
    unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
    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];
    }

    NSLog(@"years:%d", years);

    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 if ([dateComponentsNow year] > [dateComponentsBirth year] && [dateComponentsNow month] == [dateComponentsBirth month]) {
        months = 11;
    } else {
        months = [dateComponentsNow month] - [dateComponentsBirth month];
    }

    NSLog(@"months:%d", months);

    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 %@", days, NSLocalizedString(@"day", @"day")];
        } else {
            return [NSString stringWithFormat:@"%d %@", days, NSLocalizedString(@"days", @"days")];
        }
    } else if (years == 0) {
        if (months == 1) {
            return [NSString stringWithFormat:@"%d %@", months, NSLocalizedString(@"month", @"month")];
        } else {
            return [NSString stringWithFormat:@"%d %@", months, NSLocalizedString(@"months", @"months")];
        }
    } else if ((years != 0) && (months == 0)) {
        if (years == 1) {
            return [NSString stringWithFormat:@"%d %@", years, NSLocalizedString(@"year", @"year")];
        } else {
            return [NSString stringWithFormat:@"%d %@", years, NSLocalizedString(@"years", @"years")];
        }
    } else {
        if ((years == 1) && (months == 1)) {
            return [NSString stringWithFormat:@"%d %@ %d %@", years, NSLocalizedString(@"year and", @"year and"), months, NSLocalizedString(@"month", @"month")];
        } else if (years == 1) {
            return [NSString stringWithFormat:@"%d %@ %d %@", years, NSLocalizedString(@"year and", @"year and"), months, NSLocalizedString(@"months", @"months")];
        } else if (months == 1) {
            return [NSString stringWithFormat:@"%d %@ %d %@", years, NSLocalizedString(@"years and", @"years and"), months, NSLocalizedString(@"month", @"month")];
        } else {
            return [NSString stringWithFormat:@"%d %@ %d %@", years, NSLocalizedString(@"years and", @"years and"), months, NSLocalizedString(@"months", @"months")];
        }

    }

}

Initial code and idea has been taken from Hamish Rickerby