AHARGANA 3 days are said to have commenced with Friday and at sunrise (at Lankā).¹ The above rule tells us how to determine the number of mean civil days elapsed at mean sunrise at Lankā on the given lunar day (tithi) since the beginning of Kaliyuga (when all the planets were in conjunction at the first point of the asterism Aśvini). According to Aryabhata I and Bhaskara I, the duration of Kaliyuga is 10,80,000 years and it began on Friday, February 18,, B.C. 3102, at sunrise at Lanka in the beginning of the month Caitra. The Saka Era, which is usually used in Hindu astronomy for reckoning the years, commenced 3179 years after the beginning of Kaliyuga. Caitra is the first month of the year. The months in Hindu astro- nomy are reckoned from one new moon to the next. The yuga is a period of 43,20,000 years. At the beginning and end of a yuga the planets together with the Moon's apogee and ascending node are supposed to be in general conjunction. The number of intercalary months in a yuga denotes the excess of the number of lunar months in a yuga over the number of solar months in a yuga. The number of omitted lunar days in a yuga is equal to the number of lunar days in a yuga minus the number of civil days in a yuga. The number of intercalary months, omitted lunar days, etc., in a yuga are given in the seventh chapter³. In the rule stated above, the given true lunar month is treated as a mean lunar month and the given true lunar day is treated as a mean lunar day. The following is an explanation of the above rule: K A 3 L S s A Fig. 1 Let K denote the beginning of Kaliyuga; AA', the current mean lunar month; L, the beginning of the current mean lunar day; and s, the mean sunrise on that day. Also let S denote the beginning of the corres- ponding mean solar month; and s', the beginning of the mean solar day ¹ The same rule occurs also in LBh, i. 4-8 and TS, i. 23-26 (i). For other similar rules, see SuSi, i. 47-50; BrSp Si, i. 29-30, 34 (i); ŠiDV, I, i. 15-17; MSi, i. 21-22; Sise, ii. 15-17; Sisi, I, i (c), -3; SiSä, i. 44-47. Lankā is a hypothetical place where the Hindu prime meridian ("the meridian of Ujjain") intersects the equator. 3 See verses 1-8.
- That is to say, if A is the beginning of the tth mean lunar month,
then S is the beginning of the tth mean solar month.
