time
This function returns the number of non-leap seconds since January 1, 1970, UTC.[10] The returned value is suitable for feeding to gmtime and localtime, and for comparison with file modification and access times returned by stat, and for feeding to utime - see the examples under utime.
[10] Also known as the "epoch", not to be confused with the "epic", which is about the making of UNIX. (Other operating systems may have a different epoch, not to mention a different epic.)