Sanskrit kalpa, Pāli kappa — the cosmic aeon, the unit of time the Hindu and Buddhist cosmologies use to scale the path. A standard mahā-kalpa is the duration of one full cycle of cosmic formation, persistence, dissolution and emptiness, with stock lengths of ~4.32 billion years per kalpa in the Hindu reckoning. The unit's working role in the contemplative literature is to hold the path's timeline open at a scale large enough to make the long forms of practice the traditions prescribe — the *bodhisattva* vow, the Jain ascetic curriculum, the Theravāda