Rutu refers to the concept of seasons within various ancient Indian calendars. The term is utilized across several regions, including India, Bangladesh, Nepal, and Sri Lanka. In these traditions, a year is divided into 12 months, with each month associated with its own specific season. There are six distinct ritus in total.
The word originates from the Vedic Sanskrit term Ṛtú, which signifies a fixed or appointed time, particularly regarding the proper timing for rituals or sacrifices (yajna) in the Vedic religion. This etymology is derived from the word Ṛta, which literally translates to the "order or course of things." The term remains widely used across nearly all Indian languages.