Time Enclosed in Space

Just imagine that besides past, present, and future, there are three more time intervals:
past-present, past-future, and present-future. Four people from these
time intervals found themselves in zero time, and they need to get to
their own epoch. What will they tell about their transitions? How
will they get to their own time? Why are there four of them, given
that there are only three timelines? What is zero time, after all?