clock

Nothing: Windows and Mac are completely seperate, they each have time servers, if one is wrong alter it.

If your internet connection is active at boot, you will not see this problem.

In either OS, if time is wrong, event logs files, error messages will be out of sequence.

I tend to disable network connection when not using it but enable prior to reboot or shutdown.

farzadfrompalo alto wrote:

When I change the windows time, mac time changes! so they are not seperate

Then something is very wrong, forget the time and find out what is really happening.