Our universe has 4 dimensions, 3 spacial and 1 temporal. We can add another spacial dimension and use math to explore it. I cannot think of any reason why we cannot add add another temporal dimension in the same way. So, what would a universe with 2 temporal dimensions be like?
These are some thought I had about physics in 2 temporal dimensions.
With one spacial dimension, forwards is the only movement possible. With two spacial dimensions, movement in many different ways is possible. It would follow then that with two temporal dimensions time travel in many different 'directions' would be possible.
The formula for velocity is displacement/time. With two times, how would velocity be effected? What would happen to light, which must travel at a constant speed?
Frankly, I have no idea a universe with 2 times is like, but I very much would like to know.