CFAbsoluteTimeGetCurrent ()

Absolute time is measured in seconds relative to the absolute reference date of Jan 1 2001 00:00:00 GMT. A positive value represents a date after the reference date, a negative value represents a date before it. For example, the absolute time -32940326 is equivalent to December 16th, 1999 at 17:54:34. Repeated calls to this function do not guarantee monotonically increasing results. The system time may decrease due to synchronization with external time references or due to an explicit user change of the clock.

试试这个:

NSDate * timestamp = [NSDate dateWithTimeIntervalSince1970:[[NSDate date] timeIntervalSince1970]];

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"YYYY-MM-dd HH:mm:ss.SSS"];

NSString *newDateString = [dateFormatter stringFromDate:timestamp];
timestamp = (NSDate*)newDateString;

在本例中，dateWithTimeIntervalSince1970与格式化程序@"YYYY-MM-dd HH:mm:ss结合使用。它将返回带有年、月、日的日期和带有小时、分钟、秒和毫秒的时间。参见示例:"2015-12-02 04:43:15.008"。我使用NSString来确保格式之前已经写过。

如果你不想包含Quartz框架，[NSDate timeintervalsincerely eferencedate]是另一个选项。它返回一个double，表示秒数。

It may be useful to know about CodeTimestamps, which provide a wrapper around mach-based timing functions. This gives you nanosecond-resolution timing data - 1000000x more precise than milliseconds. Yes, a million times more precise. (The prefixes are milli, micro, nano, each 1000x more precise than the last.) Even if you don't need CodeTimestamps, check out the code (it's open source) to see how they use mach to get the timing data. This would be useful when you need more precision and want a faster method call than the NSDate approach.

http://eng.pulse.me/line-by-line-speed-analysis-for-ios-apps/

如果你正在考虑使用这个相对定时(例如游戏或动画)，我宁愿使用CACurrentMediaTime()

double CurrentTime = CACurrentMediaTime();

哪一种是推荐的方式;NSDate从网络的同步时钟中提取，并且在与网络重新同步时偶尔会打嗝。

它返回当前的绝对时间，以秒为单位。

如果你只想要小数部分(通常在同步动画时使用)，

let ct = CACurrentMediaTime().truncatingRemainder(dividingBy: 1)

这是我给斯威夫特用的

var date = NSDate()
let currentTime = Int64(date.timeIntervalSince1970 * 1000)

print("Time in milliseconds is \(currentTime)")

使用本网站验证准确性http://currentmillis.com/