Ritu · ऋतवः
The Six Ritus (Seasons)
Where many calendars divide the year into four seasons, the classical Sanskrit calendar uses six — each spanning exactly two Masa (months). Classical poets, especially Kalidasa in his Ritusamhara, wrote extensively about this six-fold cycle.
Why six, not four?
The four-season model (spring, summer, autumn, winter) developed to describe temperate climates further from the equator. The Ritu system instead reflects the Indian subcontinent's climate directly — most notably splitting out Varsha (the monsoon) as its own distinct season, since the arrival and departure of monsoon rains genuinely reshapes daily life across most of India in a way the four-season model doesn't capture.
See the 12 Sanskrit months that group into these six Ritus.