Cultural astronomy is an integral part of life. It manifests itself in connecting the sky with life-sustaining forces, fixing the calendar, celebration of the cardinal points and in keeping with seasonal changes in the agricultural cycle. As the year passes, the point of sunrise in the east moves from north-east to south-east and then returns to start the next cycle. The Sun rises exactly in the cardinal East on two occasions in a year, on 21 March and 22 September. That is equinox time when day and night are equal. The day of the northernmost point of sunrise is that of the Summer Solstice (21 June). The day of the southernmost point of sunrise is that of the Winter Solstice (21 December) after which the Sun moves northwards.Many cultures the world over celebrate the Sun's passage through the cardinal points in several different ways. For example, ournavaratras are essentially a celebration of the equinoxes whereas the annual MaghMela at Prayag is a celebration of the Winter Solstice that goes on through the entire month.
What Calendar Do You Use?
The VisnuPurana (275-325 CE) states that on the Visuva (equinox) day, the Sun enters Tula (Libra) or Mesha (Aries) rashiand then day and night have equal duration.At the start of Uttarayana (northwards movement), the Sun enters Makararashi (Capricorn) and moving through the consecutive zodiacs turns dakshinayana (southwards) after transiting into the Karkarashi (Cancer). The fact is,theevents have been drifting apart.In over 1700 years, the gap has widened to over three weeks in time. The Sun turns northwards after the Winter Solstice but it enters Makara middle of January and the MakaraSamkranti andthe Uttarayana continue to remain tied.
Beginning of the year
The periodicities in the sky form the basis of the calendar that delineates our routine. In the Vedic times, the year began on one of the cardinal days. The VedangaJyotish(VJ) is our oldest astronomy text, composed by Lagadhca. 1180 BCE.It specifiescalendric rules saying that a yuga(of five years) commences from the shuklapratipada (i.e., first day) of the Magha month with the Sun and the Moon both in the nakshatraSravistha (later named Dhanishtha;identified with the prominent stars of the Delphinus constellation) and when the Winter Solstice (WS) also takes place. The calendrical system ruled until the times of the Satavahanas (ca. 200 CE). The latter part of the Vedanga period, namely, the period 100-400 CE saw a gradual improvement in our astronomical knowledge during which the Vedanga gave way to the Siddhanta system.In this,Surya Siddhanta (SS; 400 CE, onwards) is an important tract on mathematical astronomy.Realizing that the year no longer was beginning from the Winter Solstice as that point had receded, the earliest SuryaSiddhanta astronomers sought to remedy the discrepancies by shifting the beginning of the year to or near the Vernal Equinoctial point (21 March)that had by now moved to occur near the nakshatraAshvini.
The Indian calendar has been of two kinds, the solar and the lunar with different days of start. The Hindu religious calendar is luni-solar. Here the seasons are fixed by the solar but the dates are fixed as per the lunar calendar which is pegged on to the former. The week-day system is of foreign origin. It was formally introduced in the Christian world by the Roman Emperor Constantine in 321 CE.The zodiacs are not an indigenous concept either. These were introduced into India in the Ist Century CE through indigenization of an astrological work from Alexandria.
In calendar keeping, how do we make chronological reference to events in the past? The use of an era to put events on record - the date, day, month and the year,was not there in place in the early times in India.The eras initially were regnal, referring to the day of coronation of a king. The continuous reckoning for such record started from the period of the Kushan and the Saka kings, between 100 BCE - 100 CE. Ever since, several eras have been in use in the country.
Surya Siddhantanot only describes movement of planets in the sky, it has its own definition of the Kaliyuga. It says that at the end of the last Krtayuga, all the planets with their apses and nodes came together at a specified point,the beginning of the first zodiac Mesha (Aries)on the path of the Sun and commenced their movement. The planets return to the same point after a certain fixed interval of time. The epoch of the last such conjunction is the determining point of the current Kaliyuga. Following the SS to count the number of days elapsed since the last general conjunction of the mean planets until present, the instant of the current Kaliyuga has been calculated. In the modern timekeeping, it is the midnight of February 17/18, 3102 BCE (i.e., -3101). The concepts of PuranicKaliyuga and the astronomical Kaliyuga stand on different grounds.The Kali-counting is purely an astronomical facility and is neither religious nor region specific. It was first introduced by Aryabhatta (476-550 CE) in his work Aryabhatiya (499 CE) and is used in the panchangas.
The Vikrama era, named so after a king Vikramaditya of Ujjain, is widely used in the north-western states of India. The zero year of the Vikrama era is 58 BCE (-57) but its origin is not clear. There is no historical king Vikramaditya to be found in that period. Its use is seen in inscriptions from the ninth century only. Here, the year begins from the new moon of Chaitra.
Today, we chiefly use the Christian era,and the Hijri era which are of foreign origin, and, the Saka era, the VikramaSamvat, the Kollam, etc. which are Indian. The Christian era that is supposed to start from the year of Jesus Christ actually came in use only by 532 CE. The Hijri or the Islamic Calendar is a lunar,where the year is of 12 months (354 days). The first year of the Hijri Calendar began in 622 CE. The zero year of the Saka era is 78 CE. It commences on the day following the Vernal Equinox. After Varahamihira (d. 587 CE)the Indian panchanga makers have used the Sakaera for their calendric calculations. After Independence, there were many calendric systems in use in India that often disagreed. This led the Government of India to form a Calendar Reform Committee. On the basis of its report of 1955, the Sakawas accepted as India's official civil calendar.