Time difference of 15 mins

I have searched the forum, and couldn’t find any answer for my problem, so apologies if this has already been posted.

One of my Notes client users (6.5.1) has a 15mins time difference from the operating system time. I have checked all the settings in location, notes.ini, preferences and compared to my own settings and so far they all seem identical. I have confirmed that the location is set to use the operating system settings.

Does anybody know where this client might be picking up the incorrect time from and how I can rectify it?

Thanks in advance

Debbie Rutherford