NSTimeInterval的使用

第一种方式： 
NSTimeInterval time = ...; 
NSString *string = [NSString stringWithFormat:@"%02li:%02li:%02li", 
                                              lround(floor(time / 3600.)) % 100, 
                                              lround(floor(time / 60.)) % 60, 
                                              lround(floor(time.)) % 60]; 

第二种方式： 
// You could also have stored the start time using 
    // CFAbsoluteTimeGetCurrent() 
    NSTimeInterval elapsedTime = [startDate timeIntervalSinceNow]; 

    // Divide the interval by 3600 and keep the quotient and remainder 
    div_t h = div(elapsedTime, 3600); 
    int hours = h.quot; 
    // Divide the remainder by 60; the quotient is minutes, the remainder 
    // is seconds. 
    div_t m = div(h.rem, 60); 
    int minutes = m.quot; 
    int seconds = m.rem; 

    // If you want to get the individual digits of the units, use div again 
    // with a divisor of 10. 

    NSLog(@"%d:%d:%d", hours, minutes, seconds) 

如果您有您初始日期存储在 NSDate 对象时，您可以获得新日期任何时间间隔在未来。只需使用 dateByAddingTimeInterval: 像这样： 

NSDate * originalDate = [NSDate date]; 
NSTimeInterval interval = 1; 
NSDate * futureDate = [originalDate dateByAddingTimeInterval:interval]; 

ios获取自1970年以来的毫秒数同java的System.currentTimeMillis() 

 + (NSString*)generateTimeIntervalWithTimeZone
 {
     NSMutableString *result = [[NSMutableString alloc] init];
     NSDate *date = [NSDate date];
     NSTimeInterval time = [date timeIntervalSince1970]*1000;//毫秒数要乘以1000
     double i=time;      //NSTimeInterval返回的是double类型


     NSDateFormatter *format = [[NSDateFormatter alloc] init];
     [format setDateFormat:@"Z"];
     NSString *timeZone = [format stringFromDate:date];
     NSString *timeIntervalStr = [NSString stringWithFormat:@"%.f", i];

     [result appendString:timeIntervalStr];
     [result appendString:timeZone];

     return result;
 }