八思巴
According to the Buddhist tradition, the original teachings of the Kalacakra were taught by Buddha himself. Nevertheless, it took more than two hundred years until the Kalacakra calendar was officially introduced as the Tibetan calendar by the ruler Drogön Chögyal Phagpa in the second half of the 13th century. Although this calendar was changed many times during the subsequent centuries, it kept its original character as a luni-solar calendar of Indian origin.