Some parallel worlds have different time-flows, like the fabled dwelling-places of the elves: those who visit them under the hill for a night return to find that years have passed in this world. Perhaps it is the gate leading between the worlds which causes the alteration. If a gate were 'misaligned', the shift from '| |' to '| \' or '| /' as it were would lead to that difference, much as a light-beam split and bent by a prism ends up taking a longer path. There might even be a mathematical function linking degree of misalignment to alteration of time-rate.
Beware of towns afflicted with Time Cancer.
For every second you progress through time, an infected town goes back 48 hours. Old buildings slowly become new, then incomplete, and finally just a frame and foundation, giant old trees turn to saplings, birds hatch into eggs.
one must not linger in a chrono-cancerous village for too long, before you know it you'll be a fetus. Tme cancer in unstoppable, no cure or treatment is knwn, it eats through the past until the inhabitants of a village turn into primordial protein ooze