Why does the Hindu calendar add an extra month?
हिंदू कैलेंडर में अधिक मास क्यों जोड़ा जाता है?
The short answer
Twelve lunar months come to about 354 days, roughly 11 short of a solar year, so without a correction your festivals would slide right through the seasons. Roughly every 32.5 months, the calendar adds an extra month to catch up. It's identified by a simple test: a lunar month during which the Sun doesn't enter a new zodiac sign.
The mismatch builds up, then gets repaid
A lunar month, new moon to new moon, averages about 29.53 days. Twelve of those give you about 354 days, and a solar year has about 365. So each year the lunar calendar falls 11 days behind the Sun, and after a little under three years it has fallen a whole month behind.
You can see what happens without a correction in the Islamic calendar, which is purely lunar: Ramadan moves through every season over about 33 years. The Hindu calendar instead ties its festivals to the seasons by adding months, much as the Hebrew calendar does.
The test: a month with no solar ingress
The Sun enters a new sign of the zodiac about once every 30.4 days, slightly longer than a lunar month. Normally one of these entries, called a sankranti, falls inside each lunar month, and that month is named for it. Every so often a new moon comes, and another new moon comes, and no sankranti has happened in between. That's your extra month. It borrows the name of the month that follows it and is called Adhik, “extra”.
In 2026 the extra month was Jyeshtha, running from mid-May to mid-June, so there were two Jyeshthas that year. The unusual reverse also exists: a month containing two ingresses is rare enough that most people will never need to know about it.
An unlucky month and a holy one at once
Popular practice treats the extra month in two ways that may seem at odds. It's called malamasa, the “impure” month, and families avoid fixing weddings or house-warmings in it. It's also called Purushottam Maas, Vishnu's own month, and many people give extra time to fasting, charity and reading scripture. A popular story has it that the extra month, unwanted by anyone, turned to Vishnu, who gave it his own name.
You'll hear this as devotion, not astronomy. The calendar's arithmetic doesn't say whether the month is good or bad.
““About every 32.5 months” sounds suspiciously exact. Does the arithmetic actually come out that way?”
- 12 lunar months
- 12 × 29.53 = about 354.4 days
- Solar year
- about 365.25 days
- Shortfall each year
- about 10.9 days
- Time to lose one month
- 29.53 ÷ 10.9 = about 2.71 years
- In months
- 2.71 × 12 = about 32.5
It does. This is an average: the real extra months come out irregularly, because they depend on the actual speeds of the Sun and Moon. Any given gap can be a little longer or shorter.
Ask your elders
“Ask your elders what they remember about the last Adhik Maas, and whether a wedding had to be moved because of it. Ask if anyone in the family did anything special that month, such as a daily reading or giving away food.”
Sources
- Spasht calendar engine (Swiss Ephemeris, Lahiri ayanamsa): Adhik Jyeshtha 2026
- Report of the Calendar Reform Committee (Government of India, 1955)
- Robert Sewell and Sankara Balkrishna Dikshit, The Indian Calendar (1896)
- Encyclopaedia Britannica, “Hindu calendar”
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