Shad Rtus (षड् ऋतवः)

Seasons in the Indian sub-continent are six in number, referred to as Shad Rtus (Samskrit: षड् ऋतवः). Seasons are related to the movement of the earth around the sun. Seasons are cyclical and refer to the time period known by special climatic conditions. As the sun travels in the ecliptic, the seasons change. There are six seasons discussed in Indian traditions and each season consists of two months. Vasanta Sampat (Spring equinox) marks the beginning of the spring season and Sharat Sampat (Autumn equinox) marks the beginning of the autumn season. Sun’s entry into the Sayana Makara rashi or Capricorn zodiac (Winter Solstice), called Uttarayana marks the beginning of the winter season, and entry into the Sayana Karka rashi or Cancer zodiac (Summer Solstice) called Dakshinayana marks the beginning of the rainy season.

To read this article in Hindi, click Six Seasons (छह ऋतुएँ)

Introduction

The rishis have preserved the entire natural heat and cold cyclic periods in one year, dividing the year into two by the difference in the movements of the sun and the moon, called Ayana. They are two ayanas - Uttarayana and Dakshinayana. In Uttarayana, the night is short and the day is long, and in Dakshinayana, the day is short and the night is long. Each of these solstices is subdivided into three divisions, called Rtus or seasons. The six main seasons in Bharatiya time reckoning are

• Uttarayana - winter, spring, and summer
• Dakshinayana - rainy, autumn, and winter

The heat of the sun reaches the earth through light and the radiation provided by the sun is the main cause of heat and cold. When we experience more heat in the sun’s radiation, we call it summer, and when we experience less, we call it autumn.

There are two types of movements of the earth, the first is the diurnal movement and the second is the annual movement. According to the diurnal motion, the earth continuously rotates on its axis from west to east, causing days and nights, and according to the annual motion, the earth continuously rotates on its axis, completing one revolution of the sun in a year, causing the formation and change of seasons. [1]

Due to the Earth's annual rotation, daily rotation, and tilt on its axis, the Earth does not experience the same weather throughout the year. Depending on the location on earth it is hot, cold, or rainy. Seasons change in every part of the earth. If seasons did not change, perhaps life on earth would not have been possible. The part of the Earth where the days are longer receives heat for a longer period from the Sun and thus that place is hot. Where days are shorter, heat is received from the sun for a shorter period. Therefore, it is cold in that particular place. [2]

Definition

इयर्ति गच्छति अशोक-पुष्पविकासान् साधारणलिङ्गमिति वसन्तादिकालविशेषऋतुः।

Synonyms of Rtu found in various texts include Kaala, Beejam, Saterakam, Samayam, and Maasadvayatmaka kala. [3]

Factors involved in formation of seasons

Many countries reckon four seasons, namely, spring, summer, fall and winter each having three months. Indian system of time reckoning has two additional seasons, rainy (Varsha Rtu) and pre-winter (Hemanta Rtu). Generally, seasons are based on solar time in Western systems of time keeping. Bharatiya Kalamana or Indian system of time keeping considers nine ways to measure time. At least five factors influence the formation of seasons.

1. Axial tilt of the earth or obliquity
2. Earth's revolution around the sun
3. Angle of sun's radiation
4. Daylight period
5. Atmosphere

Axial Tilt and Precession of Earth

Planetary bodies revolving around objects exhibit an axial tilt toward the object around which it orbits. Axial tilt refers to an imaginary axial line formed where a planet's vertical axis is tilted to a certain degree towards the ecliptic of the object it orbits (sun in the case of solar system). Also referred to as obliquity, in case of earth, it orbits the sun on a slant about 23.4 degrees. The red imaginary red line in the image is the Earth's axis. NASA's findings suggest that Uranus tilts almost 98 degrees in the solar system, and that most planets other than earth are also tilted, some more than the others.

Seasons happen because Earth orbits the sun at an angle causing variable amounts of solar radiation to reach different parts of the planet.

Due to axial tilt

- the Northern and Southern Hemispheres experience opposite seasons at the same time

- there is variation in the angle of sun's rays thereby affecting the amount of solar radiation received in any particular location

- the number of daylight hours are different at different times of the year in different places on earth, thus longer days in summer and longer nights in winter

Without axial tilt (or obliquity) day and night are not evenly divided on earth. Had earth's axis been perpendicular (no tilt) to its orbital plane around the Sun, all places on Earth would experience equal amounts of day and night (12 hours each) every day of the year. There would be no seasonal variability nor any way to measure time.

Indian astronomers, the ancient seers, however, went ahead to find the reason why the seasons changed over time. Even though the Earth's tilt is relatively stable over long periods of time, it does undergo a slight rocking or swaying motion called nutation (a nodding motion like a gyroscope). Earth's oblique axis is subject to a slight wobble (like a spinning top) which is causing its orientation to change over time. Known as Precession or Ayana (अयनम्) by Indian astronomers, this process is causing the date of the seasons to slowly change over a 25,800 year cycle. Indian astronomical treatises take into consideration, precession of the earth in the calculation of seasons and hence the system is called Sayana (Sa- along with, Ayana -precession) or tropical year. Precession is the reason for the difference between a sidereal and tropical year. The movement of the earth around the sun with constellations of stars (zodiac) as reference point where precession is not taken into consideration is called Nirayana (i.e., nir - without, ayana - precession) or Sidereal system.

Earth's Revolution

The axial tilt being largely constant (it changes over a long time period) the Earth's revolution around the sun brings about the exposure of different hemispheres being pointed towards the Sun. When the north pole is pointed towards the Sun, the northern hemisphere experiences summer and the southern hemisphere experiences winter. When the south pole is pointed towards the Sun, in the next six months the season is reversed.

Angle of Sun's Radiation

Axial tilt of the earth results in there being a difference in how much sunlight reaches a given point on the earth's surface during the course of a year. The angle at which sun's radiation falls on the earth influences seasonal temperatures.

Classification of Seasons

Seasons are classified into six types as follows

मृगादिराशिद्वयभानुभोगात् षडर्तवः स्युः शिशिरो वसन्तः। ग्रीष्मश्च वर्षाश्च शरच्च तदवत् हेमन्त नामा कथितोऽपि षष्ठः॥(बृह०अवक०)

वसन्तो ग्रीष्मसंज्ञश्च ततो वर्षा ततः शरत् । हेमन्तः शिशिरश्चैव षडेते ऋतवः स्मृताः॥

मीनमेषगते सूर्ये वसन्तः परिकीर्तितः। वृषभे मिथुने ग्रीष्मो वर्षाः सिंहेथ कर्कटे॥

शरत्कन्यातूलयोश्च हेमंतो वृश्चिके धनौ। शिशिरो मकरे कुंभे षडेवमृतवः स्मृतः॥(ज्योतिर्मयूखः) (Jyotirmayukh)

Meaning: Sayana Capricorn - Aquarius make up the winter season, Pisces-Aries the spring season, Taurus-Gemini the summer season, Cancer- Leo includes the rainy season, Virgo-Libra include the autumn season, and Scorpio-Sagittarius make up the winter season. An illustrative table of the six seasons according to various systems are summarized below.

Indian Seasons (ऋतु)	Solar Month (सौर मास)	Lunar Month (चान्द्रमास)	Vaidik Month (वैदिक मास)	Gregorian Month (ग्रेगरियन मास)	Western Seasons
वसन्त (Spring)	Pisces (मीन) Aries (मेष)	Chaitra (चैत्र) Vaishakha (वैशाख)	Madhu (मधु) Madhava ( माधव)	March (मार्च) April (अप्रैल)	Spring
ग्रीष्म (Summer)	Taurus (वृष) Gemini (मिथुन)	Jyeshta (ज्येष्ठ) Ashadha (आषाढ)	Shukra (शुक्र) Shuchi (शुचि)	May (मई) June (जून)	Summer
वर्षा (Rainy)	Cancer (कर्क) Leo (सिंह)	Shravana (श्रावण) Bhadrapada (भाद्रपद) )	Nabha (नभः) Nabhasya (नभस्य)	July (जुलाई) August (अगस्त)	-
शरद् (Autumn)	Virgo (कन्या) Libra (तुला)	Ashvin (आश्विन) Kartika (कार्तिक) (वैदिक )	Ishu (इष) Urja (ऊर्ज)	September (सितम्बर) October (अक्टूबर)	Autumn
हेमन्त (pre-Winter)	Scorpio (वृश्चिक) Saggitarius (धनु)	Margashira (मार्गशीर्ष) Paushya (पौष)	Sahaha (सहः) Sahasya (सहस्य)	November (नवम्बर) December (दिसम्बर)	-
शिशिर (Winter)	Capricorn (मकर) Aquarius (कुंभ)	Magha (माघ) Phalguna (फाल्गुन)	Tapa (तपः) Tapasya (तपस्य)	January (जनवरी) February (फरवरी)	Winter

Seasonal changes and Indian Culture

Earth's movements lead to seasonal changes, seasonal changes lead to various cultural events. Through cultural programs, our life is enlivened with fun and frolic. Dramas play a major role in the conduct of cultural events, as the plays are enacted on religious festivals.  Seasonal activities are mentioned in the plays of Kalidasa, Bhasa, etc.

Meaning of the names of the seasons

Ancient texts describe the outcome of things according to the seasons. Every animal, tree, creeper, etc. is influenced by seasons.

अर्द्धरात्रं शरत्कालो हेमन्तश्च प्रभातकः । पूर्व्वाह्णश्च वसन्तः स्यात् मध्याह्नो ग्रीष्म एव च ॥ प्रावृडरूपोऽपराह्णः स्यात् प्रदोषः शिशिरः स्मृतः॥

Spring season - Vasanta Ritu

Madhu and Madhava are the two seasons included in Vasanta ritu and derived from the word Madhu meaning honey, a kind of essence. It intoxicates trees, creepers and animals. The season in which this juice is released is called Vasanta or spring. Therefore, it is seen that in this season, even without rain, trees, plants and flowers bloom and there is madana-vikara in animals. Therefore, Ksheera Swami has said -

वसन्त्यस्मिन् सुखम् । Happiness (is enjoyed) in spring.

That is, in which animals live happily. The conclusion is that the season in which joy and sweetness abound is called spring.

Synonyms for spring are Idhmah (इध्मः), Isshya, (इष्यः) Rituraj (ऋतुराजः), Kanta (कान्तः), Kamsakh, (कामसखः) Kusumakar (कुसुमाकरः), Pikabandhava (पिकबान्धवः), Pikananda (पिकानन्दः),  Pushpakala (पुष्पकालः), Pushyamasa (पुष्यमासः), Pushpasamaya (पुष्पसमयः), Pushpasarana (पुष्पसारणः), Balanka, (बलाङ्कः) Balankaka (बलाङ्ककः), Balanga (बलाङ्गः), Vasanta, (वसन्तः) and Surabhi (सुरभिः). [3]

Summer season. Grishma Ritu

शुक्रः शोचतेः। शुचिः शोचतेर्ज्वलित कर्मणः॥ (Nirukta 2. 5. 14)

According to this etymology, the words Shukra and Shuchi are derived from Shuch Dhatu. Shuch means to burn or dry. The season in which the earth's juice (water) dries up or burns up is called summer.

Synonyms for the summer season include Akhor (आखोरः), Ushna (उष्णः), Ushnaka (उष्णकः), Ushnakala (उष्णकालः),Ushnagamana (उष्णागमः), Ushnopagama (उष्णोपगमः), Ushmaka (ऊष्मकः), Ushman (ऊष्मा(अन्), Ushmagama (उष्मागमः), Ushmayana (ऊष्मायणः), Grishma (ग्रीष्मः), Dharma (घर्मः), Tapa (तपः), Tapartu (तपर्तु), Tapasamaya (तपसमयः), Tapana (तापनः), Dinadha (दिनाघः), Padma (पद्मः) and Shuchi (शुचिः) [3]

Rainy season. Varsha Ritu

नभ आदित्यो भवति। नेता रसानाम् । नेता भासाम् । ज्योतिषां प्रणयः, अपि वा मन एव स्याद्विपरीतः। न न भातीति वा॥ (Nirukta 2. 4. 14)

Meaning: Nabha means Aditya. The period when the sun is not fully illuminated is called Nabhas. In essence, it means the substance by which essence (juice), or water, is delivered.

Synonyms for the rainy season include Abdakalah (अब्दकालः), Kalokshi (कालोक्षी(इन्), Kshari (क्षरी(इन्), Ghanagamah (घनागमः), Jaladharamalakalah (जलधरमालाकालः), Jalarnavah (जलार्णवः), Tapatyaah (तपात्ययः), Pravrit (प्रावृट् (ष्)), Pravrisha, (प्रावृषा) Meghakalagamah (मेघकालागमः), Varisha (वरिषाः(स्त्री०ब०)), Varshartu (वर्षर्तुः), Varsha (वर्षा), Varshakalah (वर्षाकालः), Varsha (वर्षाः(स्त्री०ब०)), and Varshi (वार्षी)।

Autumn. Sharad Ritu

Although both the words ish (इष्) and urj (ऊर्ज्) have the same meaning as anna (अन्न) in the Nirukta, has written in the nirukta vivrutti as follows:

इषम् अन्नम् ऊर्जम् पयोघृतादिरूपं रसं च॥(निरुक्तविवृत्ति)

Isha (इष्) means food (अन्नम्) and Urja (ऊर्ज्) means milk, ghee, etc. From these words, ish and urj, are derived isha and urja. The season in which food and milk are in a state of paripaaka or perfected in essence (in the sense of maturity, ripened) is called Sharad.

शरच्छृता अस्यामोषधयो भवन्ति, शीर्णा आप इति। (Nirukta 4. 4. 25)

According to the above etymology, it is also proved that the season in which the herbs (crops) ripen and the water (leaving behind the dirt) becomes dry, i.e., becomes clean, is called the autumn season.

The synonyms for the autumn season are Kalaprabhata (कालप्रभातः), Ghananta (घनान्तः), Ghanatya (घनात्ययः), Pravridatya (प्रावृडत्ययः), Meghanta (मेघान्तः), Varshavasanam (वर्षावसानम्),  Sharat (शरत् (द्)) or Sharad, Sharada (शरदा) and Sharad ritu (शरद् ऋतु) [3]

Hemant season Hemanta Ritu

The word Sahasa (सहस्) is expressed as strength (बल) in the Nighantu. For to endure is, alternatively, an act of strength. The words saha (सहाः) and sahasya (सहस्य) are derived from the word sahasa (सहस्). Meaning, the season in which strength is increased by the use of food grains is called Hemanta. It is a clear fact that food and drink offer more rigor and health in Hemanta than in other seasons and the working capacity of animals is also increased in Hemanta.

Synonyms for the Hemanta season are Tharamsaha (ऊष्मसहः), Prashala (childbirth) प्रशलः (प्रसवः), Praaleya (प्रालेयः), Raudra (रौद्रः), Lodhra (लोध्रः), Sharadanta (शरदन्तः), Sharadatya (शरदत्ययः), Himagama (हिमागमः), Hemanta (हेमन्तः), Haimana (हैमनः), and Haimanta (हैमन्तः) [3]

Winter season Shishira Ritu

शिशिरं शृणारोः शम्नातेर्वा।

The word tapas is made of the dhatu तपस् (tapas) used in the sense of सन्तापे (santape) meaning suffer, afflicted, and performing penance. The understanding is that the season in which the leaves of the tree fall after (previous) ripening due to the increase in temperature is called Shishira. शीर्यन्ते पर्णानि अस्मिन्निति शिशिरः। meaning withering out or falling off of worn out leaves is another etymological derivation of Shishira.

Synonyms for the winter season are vibration (कम्पनः), kottana (कोटनः), kodan (कोडनः), tapa (as) तपः(अस्), tuhinartu (तुहिनर्तुः), Shishir (शिशिरः), shita (शीतः), shikha (शैखः) Shaishirah (शैशिरः), Shaishah (शैषः), Saishah (सैषः), and Himkutah (हिमकूटः) [3]

The Importance of Seasons. The Importance of Seasons

The relationship of the seasons with human life is well established in ancient texts which reveal the significance and connections. Some of these texts include:

Ayurveda and the seasons

In Ayurveda, seasons are directly related to tridoshas (vata, pitta, kapha), rasa, rutucharya and rutus and gunatraya etc.

Tridoshas and Seasons

Vata, pitta, and kapha - these three doshas are of great importance in Ayurveda. Tridoshas are the cause of all kinds of diseases. As the Sushruta Samhita states:

इह तु वर्षाशरद्धेमन्त वसन्तग्रीष्म प्रावृषः ऋतवो भवन्ति दोषोपचय प्रकोपोपशमनिमित्तम् ।(सु०स्था० ६/१०)

Meaning the accumulation, outbreak, and remission of tridoshas occur according to the seasons as per Sushruta.

Rasa and Seasons

In Ayurveda, medicines are made from plants. The power to cure diseases in plants comes from the essence contained therein. Rasa is obtained due (to changes occurring) to time. The proportions of Rasa formed in plants depends on the seasonal variations of sunlight, air, and water etc. The importance of the seasons, is thus best explained by an Ayurvedic perspective of rasa. As stated in the Ashtangarhyudaya -

तस्मिन् ह्यत्यर्थतीक्ष्णौष्णरुक्षमार्गस्वभावतः। आदित्यपवनाः सौम्यान्क्षपयन्ति गुणान्भुवः॥

तिक्तः कषायः कटुको बलिनोऽत्र रसाः क्रमात् । तस्मादादानमाग्नेय ...।

....ऋतवो दक्षिणायनम् ।

वर्षादयो विसर्गश्च यद्बलं विसृजत्ययम् । सौम्यत्वादत्र सोमो हि बलवान् हीयते रविः।(सूत्रस्थान अ०३/३-७)

Hence, in the आदानकाल or receiving periods of time (winter, spring, summer), तिक्त, कषाय, कटुरस or the Tikta (bitter), Kashaya (astringent) and Katu (pungent) rasas are enhanced. During the विसर्गकाल, or shedding time periods (Varsha, Sharad, Hemanta) viscous लवण, आम्ल, मधुररस or salty, sour, sweet rasas are enhanced and the other rasas are depleted.

Rtucharya (Seasonal Regimen)

Ayurvedic science also gives a complete description of what activities have to be carried out in each season, what to eat in which month, and what to eat and drink under the broad heading of Rutucharya. The body is healthy and disease-free if it behaves following the system of seasonal changes.

Seasons and Three Gunas or qualities

Sattva, rajas, and tamas are the three qualities well-studied by the Acharyas in the tradition of Indian Darshanas. According to them, all worldly systems function following these three qualities. Vata, Pitta, and Kapha are the three gunas in Ayurveda. The entire medical science of Ayurveda is dependent on these three. The Darshanic qualities of sattva, rajas, tamas and vata, pitta, kapha of Ayurveda are closely associated with the seasons. Sattva, rajas, tamas and vata, pitta, kapha are always present in the body of living beings each being enhanced by depressing the other two qualities. The outburst of sattva by depressing rajas and tamas, and the same is seen in the case of vata, pitta, kapha where the outburst of one guna happens by depressing the other two. As stated about the origins of Vata Pitta and Kapha:

1.      आकाशवायुभ्यां वातः – Vata is generated from the sky and the air.

2.      अग्निजलाभ्यां पित्तम् – Pitta originates from fire and water.

3.      जलपृथिवीभ्यां कफः – Kapha is from water and earth.

Similarly -

4.      तमोबहुला पृथ्वी - The earth is rich in tamoguna.

5.      सत्त्वबहुलं पित्तम् - Pitta is rich in sattva qualities.

6.      रजोबहुलं वायुः - Vayu is rich in rajoguna.

This proves the similarity of Kapha with Tamaguna, Pitta with Sattvaguna, and Vata with Rajoguna.

Dharmashastra and Seasons

From the Dharma point of view, both Yajna-Vidhana and Vratha-Vidhana are closely related to the seasons. Such as -

Rituals and seasons

Yajnas have been arranged according to the seasons. Which yajna should be performed in which season is largely ascertained in these texts. A large tradition of Rituyagas is found in Vedic literature.

The six seasons have also been legislated by modifying the pranatva of the Rituyagas -

प्राणा वै ऋतुयाजाः ….षड् ऋतुनेति यजन्ति।

It is clear from this that the Yajna system is based on the seasons.

Vrat and Seasons

In India, the tradition of fasts and festivals is widespread. The arrangement of festivals and fasts is also according to the seasons. Fasting and related dharmic activities are closely related to each other. Vratas being a part of Dharmashastra are many but the ones depending on the seasons are as follows:

In spring - Navaratri (Ramanavami)

In summer - Harishayani Ekadashi

In the rain - Nag Panchami, Shravani, Krishna Janmashtami

In Sharad - Shardiya Navratri, (Dussehra), Deepawali, Hariprabodhini Ekadashi

In Hemant - Kaal Bhairavashtami

In Shishir - Makar Sankranti, Basant Panchami, Mahashivratri, Holikotsav

In this way, the relationship of the seasons with Ayurveda Shastra and Dharma Shastra as well as other texts is seen. Hence, human life has a special relationship with seasons. Seasons are of great importance in other aspects along with the world.

वसन्तो ग्रीष्मो वर्षा। ते देवाऽऋतवः शरद्धेमन्तः शिशिरस्ते पितरः॥(शतपथ ब्राह्मण)

According to the above verse, spring, summer, and rainy seasons are the three divine seasons and Sharad, Hemant and Shishir are the seasons of the ancestors. Hence, appropriate actions are to be undertaken for auspicious results during these seasons.

Seasonal fruits

There are six seasons: summer when sun is in Taurus and Gemini, rainy season with sun in Cancer and Leo, autumn when sun is in Virgo and Libra, autumn when the sun is in Scorpio and Sagittarius, winter when sun is in Capricorn and Aquarius and spring in the sun of Pisces and Aries.

दीर्घायुर्धनिको वसन्तसमये जातः सुगन्धप्रियो। ग्रीष्मर्तौ घनतोयसेव्यचतुरो भोगी कृशाङ्गः सुधीः॥

क्षारक्षीरकटुप्रियः सुवचनो वर्षर्तुजः स्वच्छधीः। पुण्यात्मा सुमुखः सुखी यदि शरत्कालोद्भवः कामुकः॥

योगीकृशाङ्गः कृषकश्च भोगी हेमन्तकालप्रभवः समर्थः। स्नानक्रियादानरतः स्वधर्मी मानी यशस्वी शिशिरर्तुजः स्यात्॥

Meaning - The person born in the spring season is long-lived, rich, and likes fragrances. One born in the summer season is clever, enjoys pleasurable things, lean-bodied, and erudite. A person born in the rainy season likes salty and bitter-tasting things and milk, steady minded, and is capable of talking sweetly with others. A person born in autumn is pious, talks lovingly, is happy, and lustful; a person born in the pre-winter seasons (Hemanta) is a yogi, lean-bodied, an agriculturist, prosperous, and a capable man.  A person born in the winter months follows his dharmas, regularly bathes (in rivers and tirthas) gives charity, honourable and successful.

Healthy lifestyle and diet

It is better to prevent the disease than to treat it. Good observances including seasonal regimens, day and night routines, help in disease prevention. Health is always desired by the best of men, therefore, by regular practice of the three healthy observances described in Ayurveda, a man can always be healthy. The rishis have integrated the entire period of natural cold and heat in one year in the form of seasons. Ayurveda considers these six seasons for the accumulation (Sanchay), aggravation (prakop), and remission (upashaman) of doshas.

Some essential guidelines related to Ritucharya for a healthy life-

·      Knowledge of consumables and non-consumables in a particular season.

·      Knowledge of seasons and intercalary period (Ritu-sandhikaal) of time

·      Knowledge of foods to be consumed at the beginning and end of the seasons.

·      Knowledge of seasonally favorable rasas and the related foods to be consumed.

Knowledge of the seasons related to spring, summer, rainy, autumn, pre-winter and winter seasons is helpful in leading a healthy life and lifestyle. [4]

Discussion

मधुश्च मधवश्च वासन्तिकावृतू। (यजु० १३/२५)

शुक्रश्च शुचिश्च ग्रैष्मावृतू। (यजु०१४/०६)

नभश्च नभस्यश्च वार्षिकावृतू। (यजु०१४/१५)

ईषश्चोर्जश्च शारदावृतू। (यजु० १४/१६)

सहश्च सहस्यश्च हैमान्तिकावृतू। (यजु० १४/२७)

तपश्च तपस्यश्च शैशिरावृतू। ( यजु० १५/५७)

The Taittiriya Samhita also describes these seasons in sequence and even today these seasons are prevalent in the world during these months.

The Brahma Purana describes the origin of the world by Brahma in the spring, in the month of Chaitra.

चैत्रे मासि जगति ब्रह्मा ससर्ज प्रथमेऽहनि। शुक्ले पक्षे समग्रन्तु तदा सूर्योदये सति॥ प्रवर्तयामास तदा कालस्य गणनामपि। ग्रहान् राशीनृतून् मासान्वत्सरान् वत्सराधिपान् ॥

In the Bhagavad-gita, Maharshi Vyasa describes the primacy of Kusumakar Vasanta by introducing its divine significance:

ऋतूनां कुसुमाकरः।

Consideration of spring as the beginning of the year is still prevalent today. The calendar starts from spring and Chaitra Pratipada marks the beginning of the new year. Vasanta is considered to be the King of Ritus and Sharadrutu is considered to be the mother of the Vaidyas in Ayurveda.

वैद्यानां शारदी माता पिता तु कुसुमाकरः।

In the Shatapatha Brahmana, it is written about the seasons as follows:

वसंतो ग्रीष्मो वर्षाः। ते देवा ऋतवः। शरद्धेमंतः शिशिरस्ते पितरो स(सूर्यः) यत्रोदगावर्तते। देवेषु तर्हि भवति यत्र दक्षिणावर्तते पितृषु तर्हि भवति॥(शत० ब्रा०२/१/३)

Meaning - Spring, summer, and rainy are considered as Seasons of the Devatas. Sharad, Hemant, and Shishir are the Seasons of Pitrs. When the sun is in the north (northern travel), the seasons are counted for the Devas and when in the south (southern travel), they relate to forefathers.

This shows that according to the Shatapatha Brahmana, Uttarayana took place when the sun rose from the east point to the north.

Taittiriya Samhita mentions that for 6 months the sun travels northerly and for 6 months southenly.

तस्मादादित्यः षण्मासो दक्षिणेनैति षडुत्तरेण॥ (तै०सं० ६, ५, ३)

Meaning - Therefore Aditya (Sun) remains in Dakshinayana for six months and in Uttarayana for six months.

Quote References

7.      ^ Jyoti Ray, Vedic Astrology Modern and Scientific Analysis, 2007, VBS Purvanchal University (Research Ganges) Chapter 03, (p102).

8.      ^ Rameshwar Prasad Sharma, Geographical Explanation in Indian Astrology, 1995, Dr. B.R. Ambedkar University Agra, (Research Ganga), Chapter 02, (pp. 75).

9.      ↑ 3.03.13.23.33.43.5ड Dr. Surkant Jha, Jyotir Vigyan Dictionary, 2009, Varanasi: Chowkhamba Krishnadas Academy, Kalasarg, (pp. 15).

10.  ↑ Shri Anasuya Prasadji Maithani, Arogya Anka, Knowledge of Menstruation for Healthy Living, 2007, Gorakhpur: Gitapress (pp. 1).