iOS：NSDate的主要几种时间形式

1     //获取当前日期
2     NSDate *date = sender.date;
3     NSLog(@"%@",date);

1 　　//date转字符串
2     NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
3     //YYYY:年 MM:月 dd:日 HH：24小时制  hh：12小时制
4     formatter.dateFormat = @"YYYY-MM-dd HH:mm:ss";
5     NSString *strdate = [formatter stringFromDate:date];
6     NSLog(@"%@",strdate);

1     //字符串转date
2     NSDate *date2 = [formatter dateFromString:strdate];
3     NSLog(@"%@",date2);

1     //将日期分解为年月日
2     NSCalendar *calendar = [NSCalendar currentCalendar];
3     NSInteger unitflags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
4     NSDateComponents *components = [calendar components:unitflags fromDate:date];
5     NSLog(@"year:%ld  month:%ld  day:%ld",[components year],[components month],[components day]);

1     //将年月日组合成日期
2     [components setYear:2014];
3     [components setMonth:9];
4     [components setDay:1];
5     NSDate *date3 = [calendar dateFromComponents:components];
6     NSLog(@"%@",date3);