ios-时间设置和格式输出

NSDate

NSCalendar 

NSDateFormatter 

         NSDate *now=[NSDate date];
        NSCalendar *cal=[[NSCalendar alloc]
                         initWithCalendarIdentifier:NSGregorianCalendar
                         ];
        [cal setTimeZone:[NSTimeZone systemTimeZone]]; // 3
        NSDateComponents *dc = [cal components:(NSHourCalendarUnit|NSMinuteCalendarUnit|
                                                     NSSecondCalendarUnit) fromDate:now];  // 4
        //now  2013-06-13 05:45:43 +0000
          NSLog(@"The time is%@",now);
        NSLog(@"The time is%d:%d:%d",[dc hour], [dc minute], [dc second]); // 5
        NSDateFormatter *dateFormatter=[[NSDateFormatter alloc]init];
        [dateFormatter setAMSymbol:(@"AM")];
        [dateFormatter setPMSymbol:@"PM"];
       // [dateFormatter setDateFormat:@"yyyy-MM-dd"];
      [dateFormatter setDateFormat:@"dd/MM/yyyy hh:mmaaa"];
        
        NSDate *curDate=[NSDate date];
        NSString *str=[dateFormatter stringFromDate :curDate];
        NSLog(@"%@",str);
        NSCalendar *c=[NSCalendar currentCalendar];
        unsigned int unitFlags=NSYearCalendarUnit|NSMonthCalendarUnit|
        NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit;
        NSDateComponents *dd=[c components:unitFlags fromDate:curDate];
        int y=[dd year];
        int d=[dd day];
        NSLog(@"%d 年 %d日",y,d);