Kalachakra

The Tibetan astronomical system and calendar making is based on the Sri Kalachakra Tantra (Wheel of Time Tantra), which was translated into Tibetan from Sanskrit in 1027 A.D. This highlevel Buddhist teaching has three chapters, of which astrologicaly speaking, the first is the most interesting. 

1. External Kalachakra. 
External Kalachakra presents Tibetan cosmology. It focuses on 
the creation of the Universe, the movements of the planets and stars, the five elements and chronological studies. The year is constituted by the Sun's movement trough the astrological signs. When the Sun is entering into Aries it also marks the Kalachakra New Year, which is actually the third month of the Tibetan Calendar. The eclipse of the Sun is explained by Tibetan cosmology in the same way as modern western astronomy i.e. that the Moon comes between the Earth and the Sun.

2. Internal Kalachakra.
Internal Kalachakra focuses on chakras (energy centres of the body), its energy channel system and how external forces, such as planets and stars, affect the body.

3. Alternative Kalachakra.
Alternative Kalachakra is about high-level meditation, yoga practice, empowerment teachings, taking of initiation and the visualisation of one's own personal deity.