Buddhism kept the word kalpa and abandoned the arithmetic. Asked how long an aeon lasts, the Buddha of the Pali Canon declines to answer in years and offers similes instead. One: suppose a mountain of solid rock, a league high and a league around, and once a century a man strokes it with a fine cloth; the mountain would be worn away before the aeon ends. Another: a walled city filled with mustard seeds, one seed removed each century, is emptied sooner than the aeon passes. The rhetorical strategy is deliberate.
Where the Hindu Puranas convert cosmic time into exact and enormous figures, the Buddhist texts convert it into felt duration, numbers being too easily said and too little imagined. The commentarial tradition, systematized in works like the Visuddhimagga, did add structure: great aeons divided into incalculable epochs of world contraction and expansion, aeons in which no Buddha arises and rare fortunate aeons, like the present one, in which several appear. But the similes remain the tradition's signature, and they serve its soteriology: the point of the mountain and the mustard seeds is that beings have already wandered through aeons beyond counting, shedding more tears, the texts say, than the water in the four oceans, and that the only sane response to time on this scale is not awe but urgency about release. Jainism, for its part, stretched the same word across its own endless rising and falling half-cycles, agreeing with both neighbors that the world's clock dwarfs the human one.