My PC time is adjusted automatically to a time server. However, the
time server is a few minutes ahead of the actual time and I have no
means to correct the timer server. And the firewall blocks me from
synch with a external timer server.

Is there any (commandline) utility that I can run at start up so that
it can adjust the time back by a few minutes and seconds (rather than
setting a actual time).

The sync to the time server is for signon purpose. But I think a few
minutes would affect the signon.

Thanks.