Theme revealed usually slightly before the jam officially starts so most timezones would be included and will have a fair start.
If you are new to the competition I would highly recommend to watch previous years videos on xanderwood's channel :)
And also, focus on the task, don't overscope, keep it very simple and to the point of the task. Then you are most likely will get to the next round. With next rounds the competition would get tighter and you will be able to show your game dev skills in full :)
In general two weeks is very good time to develop a playable build which will be task related :)