Adhik Maas Explained: Why Does an Extra Month Occur?

Adhik Maas (अधिक मास, "extra month"), also called Purushottam Maas or Malmas, is an inserted 13th lunar month that appears in the Hindu calendar roughly every 32–33 months. It's the same basic idea as a Gregorian leap year's extra day — a periodic correction that keeps a calendar aligned with the astronomical year it's meant to track — just on a much larger scale.

The core problem it solves

Twelve lunar months (each averaging about 29.5 days) add up to roughly 354 days — about 11 days shorter than the 365-day solar year. This gap exists because the Moon's orbital period and the Earth's orbital period simply aren't neat multiples of each other; it's a basic astronomical fact, not a design flaw. Left uncorrected, a purely lunar calendar drifts through all four seasons over time — exactly what happens in the Islamic Hijri calendar, which has no such correction and cycles through the seasons over roughly 33 years.

Why the Hindu calendar corrects for this

Because Hindu festivals and agricultural/ritual timing are meant to stay anchored to specific seasons — Vasant Panchami to spring, Sharad Purnima to autumn — the calendar needed some mechanism to prevent lunar drift from eventually detaching festivals from their intended season entirely. Adhik Masa is that mechanism: by inserting a whole extra lunar month periodically, the 11-day annual shortfall is corrected in one larger jump, roughly every 2.7 years.

The maths behind "roughly every 32–33 months"

The 11-day annual gap accumulates until it's large enough to constitute a full extra lunar month (about 29.5 days). Dividing 29.5 by 11 gives roughly 2.7 years, or about 32–33 months — which is why Adhik Masa doesn't occur on a perfectly fixed schedule (like every 3rd year exactly), but at intervals that vary slightly depending on the precise astronomical timing in a given cycle.

How the calendar decides which month becomes the "extra" one

An Adhik Masa occurs specifically in whichever lunar month contains no Sankranti (no solar transit into a new zodiac sign) — an event that normally occurs once in every lunar month. Because a lunar month is slightly shorter than the time the Sun takes to move through one zodiac sign, occasionally an entire lunar month passes without a Sankranti falling inside it; that month gets "repeated," with the repeated occurrence named Adhik ("extra") and placed before the regular occurrence of that month's name. See our how Sanskrit months work page for the underlying month mechanics this builds on, or the Sanskrit months reference for all 12 names.

Adhik Masa vs a normal lunar month

An Adhik Masa carries the same name as the regular month it precedes or follows (an "Adhik Ashadha" is immediately followed by a regular Ashadha, for instance), but is traditionally treated differently for religious observance — many new ceremonies, weddings, and other auspicious beginnings are deliberately avoided during Adhik Masa, while it's simultaneously considered a especially favourable time for spiritual practices, scripture reading, and charity, particularly associated with Vishnu (hence the alternate name Purushottam Maas, "the month of the Supreme Person").

Traditional significance, kept separate from the calendar mechanics

The astronomical explanation above — a correction for the lunar-solar year gap — is a calendar mechanics fact. Separately, many traditions attach specific religious significance and recommended practices to Adhik Masa, rooted in scripture and lineage-specific custom; these beliefs and practices vary by community and text, and this article doesn't take a position on them beyond noting that they exist alongside the astronomical explanation.

How Adhik Masa affects festival dates

In a year containing an Adhik Masa, the overall Hindu calendar effectively gets a "reset" against the Gregorian calendar — festivals that had been drifting earlier for the previous 2–3 years jump back later by nearly a month. This is exactly the mechanism explored with real 2026–2027 figures in our festival-date-shift explainer.

Is Adhik Masa the same as a "double month"?

Colloquially yes — it's often described as a month "occurring twice" in a given year, since the calendar effectively contains 13 lunar months that year instead of the usual 12. Technically, the Adhik Masa and the regular month of the same name are still two distinct lunar cycles, each with its own new-moon-to-new-moon span, simply sharing a name because neither one contains a Sankranti transition in the case of the Adhik occurrence.

Adhik Masa across different regional traditions

While the core astronomical mechanism (a lunar month with no Sankranti) is universal across the Hindu lunisolar calendar, exactly which month becomes "extra" in a given cycle, and the specific religious customs observed during it, can vary somewhat by regional Panchang tradition and by whether a community follows the Amanta or Purnimanta month-boundary convention (see our month mechanics guide for what these mean). The underlying reason for the extra month, however, is identical everywhere it appears.

A note on regional solar calendars

Adhik Masa is specifically a feature of lunisolar calendars. The solar-calendar regions of India — Tamil Nadu, Kerala and others, covered in our regional Hindu calendar guide — don't have an equivalent leap-month mechanism, since their calendars already track the solar year directly without needing a lunar-to-solar correction in the first place.