I’m not entering a game but I wonder how would it be for the next weekend jam if you make it 2 and a half days? Currently the start and end times are the same but if they were different then maybe it would help smooth out any difficulties with the day/night cycles of all the different timezones.

I think starting 1/2 a day earlier it would be of more benefit. As it is, we (in Australasia) miss out on a Friday afternoon/evening and get a Monday morning instead. I'd rather have an evening to develop than a morning (it's chaos getting kids ready for school again and heading into work). Starting 1/2 a day earlier means we get Friday evening too, and for the geeks that's a lot of programming opportunity.