首先定義NSTimer

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0target:selfselector:@selector(timerFireMethod:) userInfo:nilrepeats:YES];

- (void)timerFireMethod:(NSTimer *)timer

{

NSCalendar *calendar = [NSCalendarcurrentCalendar];

NSDateComponents *components = [[NSDateComponentsalloc]

    [components setYear:2012];

    [components setMonth:8];

    [components setDay:13];

    [components setHour:12];

    [components setMinute:0];

    [components setSecond:0];

    NSDate *fireDate = [calendar dateFromComponents:components];//目標時間

    NSDate *today = [NSDate date];//當前時間

unsignedint

     NSDateComponents *d = [calendar components:unitFlags fromDate:today toDate:fireDate options:0];//計算時間差

    auctionTime.text = [NSString stringWithFormat:@"%d

}

這樣就完成了倒計時。

不過如果有專門的伺服器時，要把伺服器和自己本機的時間差考慮進去