IOS 计算N天之后的时间

+ (NSDate *)dateAfterDays:(int)days{
    
    NSCalendar *calendar = [NSCalendar currentCalendar];
    
    unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
    
    NSDateComponents *components = [calendar components:unitFlags fromDate:[NSDate date]];
    
    [components setDay:([components day]+days)];

    return [calendar dateFromComponents:components];
}