时间戳的换算与间隔

   double dtime=[oldTime doubleValue];

    NSDate *date=[NSDate dateWithTimeIntervalSince1970:dtime];    

    NSDate* nowDate=[NSDate date];

    NSTimeZone* zone=[NSTimeZone systemTimeZone];

    NSInteger interval=[zone secondsFromGMTForDate:nowDate];

    NSDate* locationDate=[nowDate dateByAddingTimeInterval:interval];

    NSDate* date2 =[date dateByAddingTimeInterval:interval];

    float between=[locationDate timeIntervalSinceDate:date2];