Tibetan counting numbers were used before and after the creation of the United Tibetan Writing System. Mathematics, and especially geometry, has had a great impact on the unique Tibetan architecture (stupas) and craft (thangkas). Mathematics has played an important role in the creation of the Tibetan astronomy calendar, involving calculation of celestial phenomena. The Tibetan Astronomical Science - elementary (Byung-rTsis), and advanced (Skar-rTsis) - has drawn from the knowledge of neighboring countries, such as India and China, and also from Buddhists teachings to establish a unique Tibetan system.