Current Perl documentation can be found at

Here is our local, out-dated (pre-5.6) version:

Assuming you're running under sufficient permissions, you should be able to set the system-wide date and time by running the date(1) program. (There is no way to set the time and date on a per-process basis.) This mechanism will work for Unix, MS-DOS, Windows, and NT; the VMS equivalent is set time.

However, if all you want to do is change your timezone, you can probably get away with setting an environment variable:

    $ENV{TZ} = "MST7MDT";                  # unixish
    system "trn comp.lang.perl.misc";