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/
iOS.GetCurrentTimestamp,布布扣,bubuko.com
原文：http://www.cnblogs.com/cwgk/p/3818853.html