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.
Moonlight shines down on the tranquil scene of a slumbering inn along one of the many roads that cross the land. Trees sway gently in the night air, and the stars twinkle brightly. All is quiet as the PCs snore away, a fine tendril of smoke curlsrnunder their door. The tavern is on fire! This is particularly bad news if the PCs own any horses - the screaming they hear is probably from their mounts! Panicky people are rushing about with buckets of water, trying to tame the flames. The fire fighting effort is not very coordinated as everybody is either hungover or still drunk, including the PCs. Hurry!