In calculating time dilation gravity (General Relativity) and velocity (Special Relativity) must both be taken into account. As a consequence of these two variables time dilation is nearly constant over the surface of the Earth. This means that the Equator and the Poles age at the same rate.
In a case where unequal time dilation has taken place at separate locations, this does not create a duality in the present. Time dilation is not time travel. Time travel (if possible) would required exceeding the velocity of light.