Ritu (Indian season)

Ritu (Sanskrit: ऋतु, Bengali: ঋতু) defines "season" in different calendars around the South Asian countries of India, Bangladesh, Nepal and Sri Lanka, and there are six ritus (also transliterated rutu) or seasons. The word is derived from the Vedic Sanskrit word Ṛtú, a fixed or appointed time, especially the proper time for sacrifice (yajna) or ritual in Vedic religion; this in turn comes from the word Ṛta (ऋत), as used in Vedic Sanskrit literally means the "order or course of things". This word is used in nearly all Indian languages.

Nepal and India observes six ecological seasons. Southern parts of India experiences the seasons on a different schedule than the one depicted here.

शरद्

हेमन्त

East Indian Hindu (Bengali and Mithila which too starts its new year from Mesh Sankranti, in fact Nepali and Assamese and Odia Hindus too do the same, the season names are in all other in Sanskrit Vasanta, Grisma, Varsha, Sharada, Hemanta, Sisira) calendar. The Bengali Calendar is similar but differs in start and end time but is more practical as Vasant Panchami falls here in Vasant but in above calendar in Shishir in fact as that Magha Shukla Panchami. It has the following seasons or ritus:

(গ্রীষ্মকাল)

(বর্ষাকাল)

(শরৎকাল)

(হেমন্তকাল)

(শীতকাল)

(বসন্তকাল)

The South Indian Hindu Tamil calendar follows a similar pattern of six seasons as described for north Indian Hindu calendars which in fact need adjustment as taking new year from Grishma like that Bengali calendar....

The seasons are described in literature such as the Sanskrit poem Ṛtusaṃhāra written by the legendary Sanskrit poet Kālidāsa.

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Wikipedia