IOS中关于日期的操作

1、获取日期中的年、月、日、时、分、秒、周

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

NSDateComponents *comps = [[NSDateComponents alloc] init];

NSInteger unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekdayCalendarUnit     | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

NSDate *now = [NSDate date];

comps = [calendar components:unitFlags fromDate:now];

week = [comps weekday]; month = [comps month]; day = [comps day]; hour = [comps hour];

min = [comps minute]; sec = [comps second];