saṃvartasthāyikalpa [alt. ṡūnyākalpa] (P. saṃvaṭṭaṭṭhāyīkappa; T. stong pa'i bskal pa སྟོང་པའི་བསྐལ་པ་; C. kongjie 空劫) is translated as "eon of voidness," "eon of nothingness," etc. It one of the four periods in the of creation and destruction of a world system, corresponding to the four divisions a great eon (mahākalpa).
Science and Philosophy in the Indian Buddhist Classics (Vol 1) states:
- The eon of voidness is said to be the period of abiding in a void state from the destruction of former worlds up until but not including the formation of future world systems. It also lasts for twenty intermediate eons.