This paper analyses the complex variety that characterises the Indian calendric system and its relation to culture, history, and society. The aim is to understand the role played in contemporary India by traditional knowledge of astral science. For this purpose, I shall investigate the information provided by a modern Hindi pañcāṅga. This denotes a traditional almanac that goes back to a well-established practice of calendar making attested in Sanskrit literature. In medieval India, the pañcāṅga forecasted celestial phenomena such as the weather and solar eclipses and was commonly used to establish the dates for religious festivals, to know auspicious moments to undertake activities such as trading, marriage, traveling, and to set up the performance of vratas (religious ceremonies) and saṃskāras (Hindu initiation rituals at important occasions of life). Different versions of pañcāṅgas are published nowadays in all the Indian regional languages and even in English by jyotiṣīs or ‘astrologers’. Since early times, festivals, rituals, and religious ceremonies have been marked in India lunar months and the passage of the seasons. The present paper shows that astrology still plays a major part in every sphere of human life and that, in the course of a month, the changing phases of the moon coincide with the ritual observance of ancient religious practices.