iOS获取系统时间

//获得系统时间  
NSDate *  senddate=[NSDate date];  
NSDateFormatter  *dateformatter=[[NSDateFormatter alloc] init];  
[dateformatter setDateFormat:@"HH:mm"];  
NSString *  locationString=[dateformatter stringFromDate:senddate];  
//[dateformatter setDateFormat:@"YYYY-MM-dd-HH-mm-ss"];  
//NSString *  morelocationString=[dateformatter stringFromDate:senddate];  
  
//获得系统日期  
NSCalendar  * cal=[NSCalendar  currentCalendar];  

NSUInteger  unitFlags = NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear;

NSDateComponents * conponent= [cal components:unitFlags fromDate:senddate];  
NSInteger year=[conponent year];  
NSInteger month=[conponent month];  
NSInteger day=[conponent day];  

NSString *  nsDateString= [NSString  stringWithFormat:@"%4d年%2d月%2d日",year,month,day]; 

//60秒倒计时

-(void)getValidateCode{

    //倒计时

    timeout=60; //倒计时时间

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);

    dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行

    dispatch_source_set_event_handler(_timer, ^{

        timeout--;

        if(timeout<=0){ //倒计时结束，关闭

            dispatch_source_cancel(_timer);

            dispatch_async(dispatch_get_main_queue(), ^{

                //设置界面的按钮显示根据自己需求设置

                [self.buttonGetCode setEnabled:YES];

                [self.buttonGetCode setTitle:@"获取验证码" forState:UIControlStateNormal];

            });

        }else{

            int seconds = timeout % 60;

            NSString *strTime = [NSString stringWithFormat:@"剩余%.2d秒", seconds];

            dispatch_async(dispatch_get_main_queue(), ^{

                //设置界面的按钮显示根据自己需求设置

                [self.buttonGetCode setEnabled:NO];

                [self.buttonGetCode setTitle:strTime forState:UIControlStateNormal];

            });

        }

    });

    dispatch_resume(_timer);

}

//获得系统时间戳

    NSTimeInterval time = [[NSDate date] timeIntervalSince1970];

    NSString *timeString = [NSString stringWithFormat:@"%f", time];

    

    NSLog(@"%@", timeString);

 时间转时间戳的方法:
     NSString *timeSp = [NSString stringWithFormat:@"%d", (long)[datenow timeIntervalSince1970]];
     NSLog(@"timeSp:%@",timeSp); //时间戳的值
  时间戳转时间的方法
     NSDate *confromTimesp = [NSDate dateWithTimeIntervalSince1970:1296035591];
     NSLog(@"1296035591  = %@",confromTimesp);
     NSString *confromTimespStr = [formatter stringFromDate:confromTimesp];
     NSLog(@"confromTimespStr =  %@",confromTimespStr);
 时间戳转时间的方法:
 NSDateFormatter* formatter = [[NSDateFormatter alloc] init];
 [formatter setDateStyle:NSDateFormatterMediumStyle];
 [formatter setTimeStyle:NSDateFormatterShortStyle];
 [formatter setDateFormat:@"yyyyMMddHHMMss"];
 NSDate *date = [formatter dateFromString:@"1283376197"];
 NSLog(@"date1:%@",date);
 [formatter release];