One of the characteristics of Purāṇās is Manvantara, which means

Manvantara is a term used in Purāṇās to describe one of its characteristics. Manvantara refers to the period of time in which a specific Manu, the progenitor of humanity, rules over the world. It is believed that each Manvantara lasts for a specific duration, which is divided into smaller units called Yugas. These Yugas are further divided into four ages - Satya Yuga, Treta Yuga, Dvapara Yuga, and Kali Yuga. Each age is said to have its own unique characteristics and qualities. The concept of Manvantara helps to explain the cyclical nature of time and the different stages of human civilization according to Hindu mythology.