If our dear earth were jarred by the impact of a large meteor, or by some other dramatic event, the tilt of the earth might change so that the north and south poles would be in new locations. The timing of the rotation of the earth on its spindle might be affected. Thus the length of each day might no longer be 24 hours as previously measured. Each calendar day might be longer, or shorter. The body rhythms, sleep patterns, migration timings and directions of us animals might be considerably affected. The number of days in a year might change, affected by the new length of day, and possibly a change in the amount of time it takes the earth to complete a circle, or orbit, around the sun. And if the earth continued to wobble for a while from the impact, it might be many years before the length of days, months, and years stabilized again. Calendar and clock makers might have a big headache, the seasons and weather might be more erratic than ever, and we might be snoozing at odd hours and walking around the block at 2 am, unable to sleep.

A sci-fi writer could have fun with such a premise.