The 13th Month in Hindu Calendar: Why Adhik Maas Exists

Have you ever looked at a calendar and noticed that festivals like Holi or Diwali don’t fall on the same date every year? Sometimes they arrive early, and other times they seem quite late. The secret behind this “shifting” schedule is the 13th month in Hindu calendar, a fascinating celestial adjustment known as Adhik Maas.

If you’ve ever wondered how many months in Hindu calendar there actually are, the answer isn’t always twelve. Every three years or so, our traditional timekeeping system hits a “reset” button. In this guide, we’ll dive into the astronomical mystery of What is Adhik Maas and why our ancestors were genius enough to invent it.

The Immediate Answer: What is the 13th Month?

In simple terms, Adhik Maas (which literally translates to “Extra Month”) is a leap month. Just like the Western calendar adds a single day to February every four years, the Hindu calendar adds an entire month every 32 to 33 months.

This extra period is also called Purushottam Maas or Mal Maas. Its job is to fix the “drift” between the cycles of the moon and the journey of the sun. Without this 13th month, our seasons would eventually flip, and we’d be celebrating the winter festival of Diwali in the middle of a scorching summer!

The Math of Time: Lunar vs Solar Year Gap

To understand why we need an extra month, we have to look at the two different ways we measure a year. Most of our modern world runs on the Solar year, but our traditions are guided by the Lunar year.

Here is the breakdown of the lunar vs solar year gap:

• The Solar Year: This is the time it takes for the Earth to orbit the Sun. It lasts approximately 365.25 days.
• The Lunar Year: This is based on 12 cycles of the moon. A lunar month is about 29.5 days, meaning 12 lunar months add up to only 354 days.

Do you see the problem? There is a gap of roughly 11 days every single year. After three years, that gap grows to 33 days—about one full month!

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The Science of Sankranti: How Astronomers “Find” the Month

Ancient Indian astronomers didn’t just guess when to add a month. They used a very precise mathematical rule based on the Sankranti. A Sankranti is the moment the Sun moves from one zodiac sign (Rashi) to the next.

Usually, every lunar month has one Sankranti. However, because the moon moves faster than the sun, a lunar month eventually occurs where the Sun stays “stationary” in the same zodiac sign the whole time.

When a lunar month passes without the Sun entering a new sign, it is labeled as “Adhik” or extra. This isn’t just tradition; it is a sophisticated method of solar synchronization that keeps the lunar calendar perfectly aligned with the seasons of the Earth.

Why the Number 33 is Important

If you are a student of history, you might notice the number 33 appearing often during Adhik Maas rituals. There is a beautiful mathematical reason for this.

Since the lunar year loses 11 days every year, after three years, we have “saved” 33 days. In many regions, people celebrate this “gift of time” by giving 33 sweets or 33 gifts to charity. It is a way of acknowledging that the universe has given us an extra 33 days to improve ourselves.

Purushottam Maas: The Story of the Rejected Month

There is a touching story in our folklore about why this month is so special. Long ago, it was said that every month had a presiding deity, but the 13th month was ignored and called Mal Maas (the “unclean” month) because it didn’t have a name.

Feeling sad, the month went to Lord Vishnu for help. Vishnu was so moved by its plea that he gave the month his own name: Purushottam. He declared that while this month is not for material things like weddings or new houses, it is the best month for spiritual growth, meditation, and kindness.

2026: The Next 13th Month is Coming!

If you are planning your calendar for the next few years, you should know that 2026 is an Adhik Maas year. Specifically, it will be an Adhik Jyeshtha Maas.

The dates for this upcoming 13th month are:

• Start Date: May 17, 2026
• End Date: June 15, 2026

Because of this extra month in early 2026, many of the festivals that follow—like Shravan and Diwali—will feel a bit later than usual on the English calendar. It is a great time to observe how the lunar drift is corrected in real-time!

Adhik Maas vs. The Western “Blue Moon”

Students often ask if Adhik Maas is the same as a “Blue Moon.” While they aren’t exactly the same, they are cousins in the world of astronomy.

A “Blue Moon” is when a single English month (like August) has two full moons. Similarly, Adhik Maas happens when a solar period contains two new moons (Amavasyas). Both concepts are nature’s way of dealing with the fact that our months and our years don’t fit together in perfect, even numbers.

Measuring Time in Ancient India

The precision of the 13th month in Hindu calendar shows just how advanced ancient Indian time measurement was. They didn’t just use days and hours; they had units of time that were incredibly tiny and incredibly large.

• Ghati: A unit of about 24 minutes.
• Vighati: About 24 seconds.
• Truti: The time it takes to tear the softest petal of a lotus—about 1/300th of a second!

When you understand that Adhik Maas occurs every 32 months, 16 days, and 8 Ghatis, you realize you aren’t just looking at a calendar—you’re looking at a masterwork of cosmic math.

What Should You Do During the 13th Month?

While the 13th month in Hindu calendar is considered “inauspicious” for material events like weddings or starting a new business, don’t let that fool you into thinking it’s a “bad” month.

Think of it as a “Sabbatical” for the soul. It is a time for:

1. Self-Refinement: Reading books and learning new skills.
2. Charity (Daan): Helping those in need.
3. Reflection: Taking a break from the rush of life to think about your goals.

Conclusion: Living in Harmony with the Sky

The existence of the 13th month in Hindu calendar is a beautiful reminder that we are part of a larger, living system. We don’t just follow a static piece of paper; we follow the dance of the sun and the moon.

Learning What is Adhik Maas helps us appreciate the genius of our ancestors and the mathematical harmony of the universe. So, the next time you hear someone talking about a “leap month,” you can smile knowing that it’s just the universe taking a deep breath to make sure the seasons stay exactly where they belong.

Whether you are a student studying for an exam or just a curious learner, remember: time isn’t just something we spend—it’s something we live in rhythm with.