First we will sit and wait a day at a fixed location and observe how the times and date change.
Notice that the Mouse Date did not increment when the Mouse Time rolled over. If Mouse Time is the Local Time, then the Mouse Date is not the local date.
The Mouse Date does increment when the Screen Time rolls over. So the Mouse Date belongs to the same Time Zone as the Screen Time. If the Screen Time is the GMT, then the Mouse Date is the Date of TZ 00.
So the current theory is that the screen gives us the GMT and the mouse gives us the local time and the GMT date.