Beginning of 4 Yugas, according to Astrology

 Kṛta Yuga began on the 9th day in the bright fortnight in the month of Kārtika

Tretā Yuga began on the 3rd day in the bright fortnight in the month of Vaiśākha

Dvāpara Yuga began on the new Moon day in the month of Māgha

Kali Yuga began on the 13th day of the dark fortnight in the month of Bhādrapada