Admitting that time travelling is in apparence going forward in time but visiting moments of the past, let me explain why :
They aren't evolved enough to have the integer overflow feature :(
Unlike C or low level languages which are all perfectly well suited for writing time machines (and also millennium bugs ...).
Time is a dangerous thing, it must not be handled foolishly with 32 bit timestamps (the 2038 bug will tell us why).
I've got a startup to build and some code to write, unfortunately all these time travelling matters haven't helped ;)