iOS.GetCurrentTimestamp

The Methods to Get Current Timestamp

A. CACurrentMediaTime()

B. gettimeofday

C. CFAbsoluteTimeGetCurrent

D. [NSDate date] timeIntervalSince1970]

E. mach_absolute_time() 

Clock Time:

CFAbsoluteTimeGetCurrent [NSDate timeIntervalSinceReferenceDate] return clock time.

Clock time is synchronized with the network time signal. So, they are not suitable for timestamp.

Todo:

1. How to convert mach_absolute_time() into seconds?

Reference:

1. http://stackoverflow.com/questions/358207/iphone-how-to-get-current-milliseconds

2. http://www.alexcurylo.com/blog/2009/09/05/tip-cacurrentmediatime/

原文：http://www.cnblogs.com/cwgk/p/3818853.html