Get the time the file was accessed last time.
This file time is measured in number of seconds since January 1, 1970 00:00. Note that the different file systems store the file time with different precision. Also FAT stores the file time in local time while NTFS for example stores the file time as GMT. This function returns the value rounded to whole seconds as returned by the operating system. Some of the file systems may not store all three file time types:
Trying to get a time not defined by the file system will result undef.