17/05/2026
In the Hindu calendar, an “extra month” is called Adhik Maas (अधिक मास), also known as Purushottam Maas. It happens because the Hindu lunar calendar and the solar year are not exactly the same length.
Here’s the logic step-by-step:
1. Lunar Year vs Solar Year
The traditional Hindu calendar is mainly based on the Moon’s cycles.
One lunar month ≈ 29.5 days
12 lunar months ≈ 354 days
But the solar year (Earth going around the Sun) is:
≈ 365.24 days
So every year, the lunar calendar becomes shorter by about:
365.24 - 354 \approx 11.24
That means the lunar calendar falls behind the solar calendar by roughly 11 days each year.
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2. Accumulation of Difference
After about 3 years:
11.24 \times 3 \approx 33.72
That is almost equal to one full lunar month (~29.5 days).
So instead of letting festivals drift across seasons, the calendar inserts one additional month.
This extra month is called:
Adhik Maas
Malamas (older term)
Purushottam Maas (Vaishnav tradition)
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3. How Is It Decided Astronomically?
A Hindu lunar month is connected with the Sun entering zodiac signs (Sankranti).
Normally:
One lunar month contains one Sankranti.
But sometimes:
A lunar month begins and ends without any Sankranti.
When this happens, that month becomes Adhik Maas.
So the extra month is not arbitrary — it is based on actual Sun–Moon movements.
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4. Example
Suppose there are:
Two consecutive “Shravan” lunar cycles,
but the Sun does not change zodiac sign during one of them.
Then:
First becomes Adhik Shravan
Second becomes normal Shravan
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5. Why Is It Important?
Without Adhik Maas:
Holi could move into summer,
Diwali into spring,
Navratri into winter.
The extra month keeps Hindu festivals aligned with seasons.
This is similar in purpose to:
Leap day (Feb 29) in Gregorian calendar,
but Hindu calendar uses an entire leap month instead of a leap day.
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6. Frequency
Adhik Maas occurs roughly:
once every 32.5 months,
or about every 2 years 8 months.
So in some Hindu years:
there are 13 months instead of 12.
This makes the lunar calendar stay synchronized with the solar cycle over long periods.