Lord Krsna appears at the end of the 28th Dwapar Yuga and then Lord Krsna again appears in the form of Sri Krsna Caitanya Mahāprabhu in the 28th Kaliyuga which is currently going on, kṛṣṇas tu bhagavān svayam. Otherwise in all other Kaliyuga, Gaur Narayana appears.