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;
}