Kalpa (Skt.; Tib. བསྐལ་པ་, Wyl. bskal pa) — an aeon, a vast period of time related to the different phases of a great universe (or trichiliocosm), according to Abhidharma literature. There are many different types of kalpas corresponding to different lengths of time such as great kalpas, intermediary kalpas, small kalpas, incalculable kalpas, bright kalpas, dark kalpas, kalpa of formation, kalpa of duration, etc.