The Hindus have had from very ancient times the system of lunisolar cycles, made by the combination of solar years, regulated by the course of the sun, and lunar years, regulated by the course of the moon, but treated in such a manner as to keep the beginning of the lunar year near the beginning of the solar year. The exact manner in which they arranged the details of their earliest calendar is still a subject of research. We deal here with their calendar as it now stands, in a form which was developed from about A.D. 400 under the influence of the Greek astronomy which had been introduced into India at no very long time previously.
The Hindu calendar, then, is determined by years of two kinds, solar and lunar. For civil purposes, solar years are used in Bengal, including Orissa, and in the Tamil and Malayāḷam districts of Madras, and lunar years throughout the rest of India. But the lunar year regulates everywhere the general religious rites and festivals, and the details of private and domestic life, such as the selection of auspicious occasions for marriages and for starting on journeys, the choice of lucky moments for shaving, and so on. Consequently, the details of the lunar year are shown even in the almanacs which follow the solar year. On the other hand, certain details of the solar year, such as the course of the sun through the signs and other divisions of the zodiac, are shown in the almanacs which follow the lunar year. We will treat the solar year first, because it governs the lunisolar system, and the explanation of it will greatly simplify the process of explaining the lunar calendar.
The civil solar year is determined by the astronomical solar year. The latter professes to begin at the vernal equinox, but the actual position is as follows. In our Western astronomy the signs of the zodiac have, in consequence The astronomical solar year. of the precession of the equinoxes, drawn away to a large extent from the constellations from which they derived their names; with the result that the sun now comes to the vernal equinox, at the first point of the sign Aries, not in the constellation Aries, but at a point in Pisces, about 28 degrees before the beginning of Aries. The Hindus, however, have disregarded precession in connexion with their calendar from the time (A.D. 499, 522, or 527, according to different schools) when, by their system, the signs coincided with the constellations; and their sign Aries, called Mēsha by them, is still their constellation Aries, beginning, according to them, at or near the star ζ Piscium. Their astronomical solar year is, in fact, not the tropical year, in the course of which the sun really passes from one vernal equinox to the next, but a sidereal year, the period during which the earth makes one revolution in its orbit round the sun with reference to the first point of Mēsha; its beginning is the moment of the Mēsha-saṁkrānti, the entrance of the sun into the sidereal sign Mēsha, instead of the tropical sign Aries; and it begins, not with the true equinox, but with an artificial or nominal equinox.
The length of this sidereal solar year was determined in the following manner. The astronomer selected what the Greeks termed an exeligmos, the Romans an annus magnus or mundanus, a period in the course of which a given order of things is completed by the sun, moon, and planets returning to a state of conjunction from which they have started. The usual Hindu exeligmos has been the Great Age of 4,320,000 sidereal solar years, the aggregate of the Kṛita or golden age, the Trētā or silver age, the Dvāpara or brazen age, and the Kali or iron age, in which we now are; but it has sometimes been the Kalpa or aeon, consisting according to one view of 1000, according to another view of 1008, Great Ages. He then laid down the number of revolutions, in the period of his exeligmos, of the nakshatras, certain stars and groups of stars which will be noticed more definitely in our account of the lunar year; that is, the number of rotations of the earth on its axis, or, in other words, the number of sidereal days. A deduction of the number of the years from the number of the sidereal days gave, as remainder, the number of civil days in the exeligmos. And, this remainder being divided by the number of the years, the quotient gave the length of the sidereal solar year: refinements, suggested by experience, inference, or extraneous information, were made by increasing or decreasing the number of sidereal days assigned to the exeligmos. The Hindus now recognize three standard sidereal solar years determined in that manner. (1) A year of 365 days 6 hrs. 12 min. 30 sec. according to the Āryabhaṭīya, otherwise called the First Ārya-Siddhānta, which was written by the astronomer Āryabhaṭa (b. A.D. 476): this year is used in the Tamil and Malayāḷam districts, and, we may add, in Ceylon. (2) A year of 365 days 6 hrs. 12 min. 30.915 sec. according to the Rājamṛigā ka, a treatise based on the Brāhma-Siddhānta of Brahmagupta (b. A.D. 598) and attributed to king Bhōja, of which the epoch, the point of time used in it for calculations, falls in A.D. 1042: this year is used in parts of Gujarāt (Bombay) and in Rājputānā and other western parts of Northern India. (3) A year of 365 days 6 hrs. 12 min. 36.56 sec. according to the present Sūrya-Siddhānta, a work of unknown authorship which dates from probably about A.D. 1000: this year is used in almost all the other parts of India. It may be remarked that, according to modern science, the true mean sidereal solar year measures 365 days 6 hrs. 9 min. 9.6 sec., and the mean tropical year measures 365 days 5 hrs. 48 min. 46.054440 sec.
The result of the use of this sidereal solar year is that the beginning of the Hindu astronomical solar year, and with it the civil solar year and the lunar year and the nominal incidence of the seasons, has always been, and still is, travelling slowly forward in our calendar year by an amount which varies according to the particular authority.[1] For instance, Āryabhaṭa’s year exceeds the Julian year by 12 min. 30 sec. This amounts to exactly one day in 1151⁄5 years, and five days in 576 years. Thus, if we take the longer period and confine ourselves to a time when the Julian calendar (old style) was in use, according to Āryabhaṭa the Mēsha-saṁkrānti began to occur in A.D. 603 on 20th March, and in A.D. 1179 on 25th March. The intermediate advances arrange themselves into four steps of one day each in 116 years, followed by one step of one day in 112 years: thus, the Mēsha-saṁkrānti began to occur on 21st March in A.D. 719, on 22nd March in A.D. 835, on 23rd March in A.D. 951, and on 24th March in A.D. 1067 (whence 112 years take us to 25th March in A.D. 1179). It is now occurring sometimes on 11th April, sometimes on the 12th; having first come to the 12th in A.D. 1871.
The civil solar year exists in more varieties than one. The principal variety, conveniently called the Mēshādi year, i.e. “the year beginning at the Mēsha-saṁkrānti,” is the only one that we need notice at this point. The The civil solar year. beginning of it is determined directly by the astronomical solar year; and for religious purposes it begins, with that year, at the moment of the Mēsha-saṁkrānti. Its first civil day, however, may be either the day on which the saṁkrānti occurs, or the next day, or even the day after that: this is determined partly by the time of day or night at which the saṁkrānti occurs, which, moreover, of course varies in accordance with the locality as well as the particular authority that is followed; partly by differing details of practice in different parts of the country. In these circumstances an exact equivalent of the Mēshādi civil solar year cannot be stated; but it may be taken as now beginning on or closely about the 12th of April.
The solar year is divided into twelve months, in accordance with the successive saṁkrāntis or entrances of the sun into the (sidereal) signs of the zodiac, which, as with us, are twelve in number. The names of the signs in Sanskṛit are as The solar month. follows: Mēsha, the ram (Aries); Vṛishabha, the bull (Taurus); Mithuna, the pair, the twins (Gemini); Karka, Karkaṭa, Karkaṭaka, the crab (Cancer); Siṁha, the lion (Leo); Kanyā, the maiden (Virgo); Tulā, the scales (Libra); Vṛiśchika, the scorpion (Scorpio); Dhanus, the bow (Sagittarius); Makara, the sea-monster (Capricornus); Kumbha, the water-pot (Aquarius); and Mīna, the fishes (Pisces). The solar months are known in some parts by the names of the signs or by corrupted forms of them; and these are the best names for them for general use, because they lead to no confusion. But they have elsewhere another set of names, preserving the connexion of them with the lunar months: the Sanskṛit forms of these names are Chaitra, Vaiśākha, Jyaishṭha, Āshāḍha, Śrāvaṇa, Bhādrapada, Āśvina or Āśvayuja, Kārttika, Mārgaśira or Mārgaśīrsha (also known as Agrahāyaṇa), Pausha, Māgha, and Phālguna: in some localities these names are used in corrupted forms, and in others vernacular names are substituted for some of them; and, while in some parts the name Chaitra is attached to the month Mēsha, in other parts it is attached to the month Mīna, and so on throughout the series in each case. The astronomical solar month runs from the moment of one saṁkrānti of the sun to the moment of the next saṁkrānti; and, as the signs of the Hindu zodiac are all of equal length, 30 degrees, as with us, while the speed of the sun (the motion of the earth in its orbit round the sun) varies according to the time of the year, the length of the month is variable: the shortest month is Dhanus; the longest is Mithuna. The civil solar month begins with its first civil day, which is determined, in different localities, in the same manner with the first civil day of the Mēshādi year, as indicated above. The civil month is of variable length; partly for that reason, partly because of the variation in the length of the astronomical month. No exact equivalents of the civil months, therefore, can be stated; but, speaking approximately, we may say that, while the month Mēsha now begins on or closely about 12th April, the beginning of a subsequent month may come as late as the 16th day of the English month in which it falls.
The solar year is also divided into six seasons, the Sanskrit names of which are Vasanta, spring; Grīshma, the hot weather; Varshā, the rainy season; Śarad, autumn; Hēmanta, the cold weather; and Śiśira, the dewy season. Vasanta begins The seasons. at the Mīna-saṁkrānti; the other seasons begin at each successive second saṁkrānti from that. Originally, this scheme was laid out with reference to the true course of the sun, and the starting-point of it was the real winter solstice, with Śiśira, as the first season, beginning then; now, owing partly to the disregard of precession, partly to our introduction of New Style, each season comes about three weeks too late; Vasanta begins on or about 12th March, instead of 19th or 20th February, and so on with the rest. It may be added that in early times the year was also divided into three or four, and even into five or seven, seasons; and there appears to have been also a practice of reckoning the seasons according to the lunar months, which, however, would only give a very varying arrangement, in addition to neglecting the point that the seasons are naturally determined by the course of the sun, not of the moon. But there is now recognized only the division into six seasons, determined as stated above.
The solar year is also divided into two parts called Uttarāyaṇa, the period during which the sun is moving to the north, and Dakshiṇāyana, the period during which it is moving to the south. The Uttarāyaṇa begins at the nominal winter solstice, The solstitial divisions of the year. as marked by the Makara-saṁkrānti; and the day on which this solstice occurs, usually 12th January at present, is still a special occasion of festivity and rejoicing; the Dakshiṇāyana begins at the nominal summer solstice, as marked by the Karka-saṁkrānti. It may be added here that, while the Hindus disregard precession in the actual computation of their years and the regulation of their calendar, they pay attention to it in certain other respects, and notably as regards the solstices: the precessional solstices are looked upon as auspicious occasions, as well as the non-precessional solstices, and are customarily shown in the almanacs; and some of the almanacs show also the other precessional saṁkrāntis of the sun.