Calendar, the day universally recognised being the civil, or sāvana, day, i.e., the natural day measured from sunrise to sunrise. The length of this perpetually varies; and since the sun may enter a sign, or in other words since the astronomical beginning of a month may take place, at any moment of the day or night, rules were laid down, which differed in different localities, as to the civil beginnings of the month, the principle in general being that it began at that sunrise which is nearest to the saṁkrānti or astronomical beginning of the month. (See § 43 below.) Purely solar reckoning has rarely been adopted except in Bengal, and, partially, in the Tamil and Malayāḷam tracts of Southern India.
15. In the rest of India, the calendar is based on luni-solar reckoning, the lunar months being fitted to the natural course of the seasons by the system of intercalation and suppression; in other terms a luni-solar reckoning was established—and that from a remote period. It is not necessary here to enter into a dissertation regarding the varying practices adopted, and it need only be mentioned that the general practice now makes the luni-solar year begin at sunrise of the day that immediately follows the moment of that new-moon which takes place next after the moment of the astronomical beginning of the last month of the sidereal solar year, i.e., after the moment of Mīna saṁkrānti in each year. This necessitates constant calculations. Since there are 365 or 366 days in the twelve solar months and only 354 days in the twelve lunar months, the luni-solar year is fitted to the sidereal solar year by a series of clear but rather complicated rules. These are fully explained in their place. The result is that the luni-solar year contains sometimes twelve and sometimes thirteen lunar months; and that it comprises a varying number of civil days, viz., either 354, 355, 383, 384 or 385 such days. In some tracts at the present time, and in more ancient days generally, the luni-solar year begins, not with the new- moon succeeding the Mīna saṁkrānti, but with the moon succeeding one of the other solar saṁkrāntis; or indeed with some tithi (see para. 18) not the first of the lunar month. For such variations it suffices to refer readers to § 52, pp. 31, 32, of the Indian Calendar.
15A. I have been urged to abandon altogether the term "luni-solar" year and substitute "lunar," on the ground that while there is a luni-solar cycle there is no such thing as a really luni-solar The term "luni-solar." year. I shall not contest the point, or attempt to justify my use of the term except from one standpoint. This volume is a continuation of the Indian Calendar, and in that volume we used the expression "solar year" to mean the duration of the twelve sidereal solar months; "lunar year" to mean the duration of twelve lunar months, each being one synodical revolution of the moon; and "luni-solar year" to mean the lunar year as adapted to the solar year and beginning, in the amānta system, with the new-moon succeeding the solar Mīna saṁkrānti of each year. Such a year, containing as it does sometimes twelve, sometimes thirteen lunar months, having been called the "luni-solar year" in the Indian Calendar, it would tend to create confusion if I were now to make a change and give it another name. Even if scientifically inaccurate the name must stand in respect of the present publication.
16. The sun's apparent (or true) and mean longitudes are measured, as stated above, from the sidereal fixed First Point of Mēsha. His apparent longitude is his real angular distance at any moment from that point, measured in the direction of his course. His mean longitude is this angular distance as it would be supposing he moved with a mean or average rate of motion, or with a velocity that never varied. At the moment when the apparent sun reaches longitude 0°, i.e., at the moment of apparent Mēsha saṁkrānti, the mean sun is some distance away. The true sun has travelled quicker than the mean sun, and the mean sun does not reach longitude 0° till after a period variously calculated by the various Hindū authorities, but always consisting of something over two days. This period we have called the "śōdhya" interval. (See § 39A below, &c.) An apparent nirayaṇa, or sidereal, saṁkrānti takes place when, measured by his apparent motion, the sun touches the first point of each fixed sidereal sign (rāśi); a mean nirayaṇa or sidereal saṁkrānti takes place when the sun, measured by his mean
