Every calendar has to solve the same problem: the moon and the sun do not agree. A lunar month, new moon to new moon, lasts about 29.5 days, so twelve of them make roughly 354 days, about eleven days short of the solar year that governs the seasons. A purely lunar calendar, like the Islamic one, accepts the drift, which is why Ramadan moves through all the seasons over about thirty-three years. A purely solar calendar, like the Gregorian, abandons the moon entirely. The Hindu calendar does neither. It keeps both, and every few years it pays the difference with an extra month, the adhika masa.
The rule for inserting it is elegant. Each lunar month is normally named for the solar transit, sankranti, that falls within it, the moment the sun enters a new sign of the sidereal zodiac. Because the lunar month is shorter than the time the sun spends in a sign, occasionally a lunar month begins and ends without any sankranti at all. That month has no solar event to give it a name, so it takes the name of the following month and is called adhika, extra. It happens roughly every thirty-two or thirty-three months. More rarely, a lunar month contains two sankrantis and a month is dropped, a kshaya masa, an event separated by long intervals.
The tradition did not treat the leftover month as a mere bookkeeping device. It is also called mala masa, the impure month, and marriages, housewarmings and other new beginnings are traditionally avoided in it. A Puranic story gives it a second identity. Rejected by every deity as the unwanted month with no ruler, it sought refuge with Vishnu, who took it as his own and named it Purushottama masa, his own title; since then it has been regarded as especially suited to devotion, charity and scriptural reading. A month that was structurally surplus became, in the calendar’s religious life, a month set apart for the highest things.
The Hindu calendar is not alone in this solution. The Hebrew and traditional Chinese calendars also add leap months to reconcile lunar months with the solar year, using their own rules. What stands out in the Indian version is how exactly it ties the extra month to the sun’s real motion rather than to a fixed schedule, and how naturally it absorbs a technical correction into devotional life. The festivals stay in their seasons, the months keep their moons, and the gap between two heavenly clocks becomes, every few years, an invitation.
Part 21 of 30 — Series V: What Time Is Made Of
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