I've done roughly 4-5 variations...

Late night/after dinner of the 24th.
12am of the 25th (continuation of party/dinner of the 24th).
One present on the 24th, rest in the morning of the 25th after waking up.
Your standard North-American-style morning of the 25th before or after breakfast.
Lunch-time of the 25th.

I think we may be doing a combo this year as we're going to be jumping around between family again. For the first time ever though, there are no Christmas decorations of any kind at my own house. No tree, no lights, nothing. It just sort of happened that way due to some recent renovations and then booking a last minute trip from which I just got back late this past weekend.

After spending a week in Jamaica, even with some lights and other decorations around, it just doesn't feel like Christmas.