the reason the mayan calender ends, is because their calculation of time would no longer apply to anything past that date. The atomic clock has already been changing.

In short, time will change.

The earth will grind to a halt, and reverse rotation.

No calender devised by man will apply after that date, because no human on this spaceship earth has ever witnessed such an event.

The great pyramid timeline
the I-ching
timewave zero
mayan calender
time, will in the most literal sense of the word, begin to shift.

Time will run out.