Some years feel like they have a "13th month." That's Adhika Masa—an intercalary lunar month that slides into the Vedic calendar roughly every 2.5 years. Why does it happen? And how do you know when it's coming? The answer lies in a simple astronomical check used by traditional Panchang makers: if no solar sign change occurs between two consecutive new moons, that entire lunar month is Adhika. Here's how to calculate it for your city and what to do when it arrives.
What Is Adhika Masa?
The intercalary month that keeps calendars aligned
Adhika Masa (also spelled Adhik Maas) is an extra lunar month inserted into the Hindu calendar. Think of it as a reset button. Twelve lunar months total around 354 days, which falls short of the 365-day solar year by roughly 11 days. Over time, that gap grows. Without correction, festivals would drift across seasons. Adhika Masa bridges that gap.
The name comes from Sanskrit: adhika means "extra" or "additional," and masa means "month." It's the same concept as leap years in the Gregorian calendar, but instead of adding a day, we add an entire lunar month.
Quick Glossary
Why Adhika Masa Exists
The math behind the 11-day gap
Here's the core problem: a lunar month spans about 29.5 days from one new moon to the next. Multiply that by 12, and you get roughly 354 days. But Earth takes 365.25 days to orbit the Sun. That 11-day difference accumulates.
After three years, you're looking at about 33 days of drift. That's enough to push festivals out of their seasonal windows. Imagine Diwali happening in September instead of October. Or Holi in January. The calendar would lose its connection to agricultural cycles and natural rhythms.
Adhika Masa resets that drift. By inserting an extra lunar month roughly every 2.5–3 years, the lunar calendar stays aligned with the solar year. It's not perfect—the exact timing varies—but it works. The pattern repeats roughly seven times in 19 years, which is why some years feel like they have that "13th month."
How Often Does Adhika Masa Appear?
Roughly every 2.5–3 years, seven times in 19 years
The frequency isn't rigid. You'll see Adhika Masa roughly every 2.5–3 years. More precisely, it shows up about seven times in a 19-year cycle. This pattern aligns with the Metonic cycle, where lunar phases repeat on the same calendar dates roughly every 19 years.
Why the variation? The Moon's orbit isn't perfectly circular, and the Earth's orbit around the Sun isn't either. These slight irregularities mean the gap between lunar and solar years isn't constant. Sometimes the drift accumulates faster, sometimes slower. When it reaches a threshold—roughly 29–30 days—an Adhika month gets inserted.
Why some years feel longer
The Decisive Rule: The Litmus Test
No solar sign change = Adhika month
Core rule for identifying Adhika Masa
If there is no solar sign change (no Sun's entry into a new zodiac sign) between two consecutive new moons, that entire lunar month is Adhika.
This is the litmus test. It works regardless of whether you follow the new-moon style (month runs new moon → new moon) or the full-moon style (day after full moon → next full moon). The astronomy is the same—only the day-to-day labels differ.
Note: This calculation is location-specific. New moon times vary by city due to longitude and timezone differences. Always compute for your specific location.
Think of it this way: normally, as the Moon completes its cycle from new moon to new moon, the Sun moves through at least one zodiac sign. But sometimes, the Moon's cycle is short enough—or the Sun's movement is slow enough—that no sign change happens. When that occurs, you've got an Adhika month.
How Adhika Month Gets Its Name
It takes the name of the following regular month
The intercalary month takes the name of the following regular month. For example, if Adhika month precedes the normal "Jyeshtha," it's called "Adhika Jyeshtha". If it comes before "Ashwin," it's "Adhika Ashwin".
This naming convention helps distinguish the extra month from the regular one. You'll see both "Adhika Jyeshtha" and "Jyeshtha" in the same year—the Adhika version comes first, then the normal one follows.
The name reflects which regular month it's preparing the calendar for, not which month it technically "belongs" to. It's a forward-looking label, helping you understand what's coming next in the cycle.
Amanta vs Purnimanta: Both Recognize Adhika Masa
New-moon style and full-moon style calendars use the same rule
In the Vedic calendar system, you'll find two main styles: Amanta (also called new-moon style, where the month runs new moon → new moon) and Purnimanta (also called full-moon style, where the month runs from the day after full moon → next full moon). Both recognize the same Adhika Masa.
Why? Because the rule is astronomical, not calendar-specific. The check is: does a solar sign change occur between two consecutive new moons? If the answer is no, that lunar month is Adhika—regardless of whether you follow Amanta or Purnimanta systems.
Think of Adhika Masa as a new-moon to new-moon overlay you can draw across your Panchang. Your Purnimanta month table can remain intact while you badge this overlay window. The astronomy doesn't care about your labeling system.
Practical tip for Panchang makers
How to Calculate Adhika Masa: Step-by-Step
A 4-step process you can trust
Calculation algorithm (4 steps)
- Get all new-moon instants for your chosen city. These mark the boundaries of lunar months.
- Check if a solar sign change occurs between each pair of consecutive new moons. A solar sign change happens when the Sun enters a new zodiac sign (e.g., Aries → Taurus).
- If none (zero solar sign changes between two new moons), mark that span as Adhika.
- Name it after the next regular month. For example, if Adhika precedes Jyeshtha, call it "Adhika Jyeshtha."
That's it. The rule is astronomical, not regional. This is the same method used by traditional Panchang makers and Vedic almanac compilers. Readers anywhere can verify this with public almanac listings or calculators that use the same rule. The tricky part is getting accurate new-moon times for your specific location—they vary by longitude and timezone.
Practical checklist
- Get new-moon times for your chosen city
- Mark Sun's sign changes (zero or one between two new moons)
- Zero = Adhika month; One = normal month
Real Examples: Adhika Masa Windows
New Delhi dates for 2026, 2029, and 2031
Example 1: New Delhi, 2026
The Adhika window runs May 17 → June 15, 2026 (new-moon to new-moon). During this period, no solar sign change occurs between the May 17 new moon and the June 15 new moon. You'll see an Adhika full moon on May 31, 2026, inside that window—a handy anchor for your timeline.
This Adhika month takes the name of the following regular month, so it's "Adhika Jyeshtha" (preceding the normal Jyeshtha that follows).
Example 2: New Delhi, 2029
The Adhika window for the spring cycle ends April 13, 2029; it begins at the previous new moon (March 14/15, local time). Your overlay is roughly March 15 → April 13, 2029.
Again, no solar sign change occurs between these two new moons, marking this as an Adhika month. It's part of the spring cycle, helping keep the calendar aligned with seasonal festivals.
Example 3: New Delhi, 2031
The late-monsoon Adhika window ends September 16, 2031; draw your overlay from the prior new moon up to that date. This falls in the monsoon-to-autumn transition period, another common timing for Adhika Masa insertions.
Why city matters in Panchang calculations
City Comparison: Same Rule, Different Clock Times
How Adhika Masa appears across major cities
The astronomical rule is universal, but new-moon times are location-specific. Here's how the same Adhika month window appears in different cities:
| City | 2026 Adhika Window Start | 2026 Adhika Window End | Notes |
|---|---|---|---|
| New Delhi | May 17, 2026 | June 15, 2026 | Based on IST (UTC+5:30) |
| Mumbai | May 17, 2026 | June 15, 2026 | Same dates, slightly different local times |
| Bengaluru | May 17, 2026 | June 15, 2026 | Timezone differences cause minor time shifts |
Note: While the dates often align, the exact clock times for new moons vary by city. Always check your city-specific Panchang for precise timings. For accurate city-wise Panchang calculations, use location-aware tools.
What Happens During Adhika Month?
Do's and don'ts for the intercalary period
Do During Adhika Month
- Worship and prayer: Focus on spiritual practices, daily pujas, and temple visits.
- Charity (daan): Give to those in need—food, clothes, or financial support.
- Study and learning: Read scriptures, learn about your traditions, study Panchang concepts and Vedic calendar systems.
- Routine activities: Work, cooking, and daily tasks continue normally.
- Regular pujas: Daily worship at home or temple remains unchanged.
Avoid During Adhika Month
- Marriages: Traditional practice advises postponing weddings and major samskaras.
- House-warming (griha pravesh): Avoid moving into new homes or conducting house-warming ceremonies.
- New business launches: Starting new ventures or major commercial activities is typically avoided.
- Major investments: Large purchases or financial commitments are often postponed.
- Upanayana and other major rites: Sacred thread ceremonies and other major life rituals are typically scheduled outside Adhika month.
Note: Practices vary by region and family tradition. Some communities are more strict, others more flexible. Consult your local Panchang and family elders for guidance specific to your situation. The general principle, rooted in Vedic tradition, is to focus on spiritual growth and avoid major life changes during this intercalary period.
Corner Case: The Rare Dropped Month
When two solar sign changes occur in one lunar month
Very rarely, something opposite happens: two solar sign changes can fall within one lunar month. When this occurs, a "dropped" month (kshaya masa) can result. This is uncommon—much rarer than Adhika Masa—but worth noting for completeness.
Think of it as the inverse problem. Instead of having a month with no solar sign change (Adhika), you get a month with two solar sign changes. In such cases, one regular month might be skipped or merged in the naming sequence. It's an edge case that traditional Panchang makers account for in Vedic calendar calculations.
For practical purposes, you're far more likely to encounter Adhika Masa than a dropped month. But knowing both exist helps you understand why the calendar sometimes has 12 months and sometimes 13—or, in extreme cases, why a month name might appear to be skipped.
FAQs
Straight answers for common questions
Q: How do I know if this year has Adhika month?
Check if there's a lunar month where no solar sign change occurs between two consecutive new moons. If you find one, that entire month is Adhika. Roughly happens every 2.5–3 years, about seven times in 19 years.
Q: What are the dates of Adhika month in my city?
Adhika Masa dates are location-specific because new moon times vary by city. For example, in New Delhi 2026, it runs May 17 → June 15 (new moon to new moon). Check your city's panchang or use a calculator that accounts for your location's longitude and timezone.
Q: What is allowed or avoided during Adhika month?
Traditionally, people avoid major life events like weddings, house-warming ceremonies, and new business launches. Focus instead on worship, charity, study, and spiritual practices. Daily activities like work, cooking, and routine pujas continue normally.
Q: How often does Adhika Masa occur?
Roughly every 2.5–3 years. More precisely, about seven times in a 19-year cycle. This happens because 12 lunar months total around 354 days, which is about 11 days short of the 365-day solar year. The gap accumulates, and Adhika Masa resets that drift.
Q: Why does Adhika Masa exist?
Twelve lunar months add up to roughly 354 days, but a solar year is about 365 days. That 11-day gap grows over time, causing festivals and seasons to drift. Adhika Masa (the intercalary month) corrects this by inserting an extra lunar month when needed, keeping the lunar calendar aligned with the solar year.
Q: Is marriage allowed during Adhika month?
Traditional practice advises avoiding marriages and other major samskaras during Adhika Masa. The focus shifts to worship, charity, and study instead. However, practices vary by region and family tradition. Consult your local panchang and family elders for guidance specific to your situation.
Q: What is the decisive rule for identifying Adhika month?
If there is no solar sign change (no Sun's entry into a new zodiac sign) between two consecutive new moons, that entire lunar month is Adhika. This is the litmus test that works for both new-moon style and full-moon style calendars.
Q: How is Adhika month named?
The intercalary month takes the name of the following regular month. For example, if Adhika month precedes the normal 'Jyeshtha', it's called 'Adhika Jyeshtha'. The astronomy is the same regardless of whether you follow new-moon or full-moon style calendars.
Q: Can Adhika month occur twice in one year?
Very rarely, if two solar sign changes fall within one lunar month, a 'dropped' month can occur. This is uncommon but worth noting for completeness. Typically, you'll see one Adhika month every 2.5–3 years.
Q: Does Adhika Masa calculation differ by city?
Yes. New moon times and sunrise-anchored observances are location-specific. For accuracy, always compute and display Adhika Masa dates by city. New Delhi, Mumbai, and Bengaluru may show slightly different clock times for the same Adhika month window due to their different longitudes and timezones.
Summary & Takeaway
- →Adhika Masa is an intercalary lunar month inserted to align the lunar calendar with the solar year.
- →Occurs roughly every 2.5–3 years (about seven times in 19 years) when no solar sign change happens between two consecutive new moons.
- →Takes the name of the following regular month (e.g., "Adhika Jyeshtha" precedes normal "Jyeshtha").
- →Works for both new-moon style and full-moon style calendars—the astronomy is the same.
- →During Adhika month, avoid major life events; focus on worship, charity, and study.
- →Calculation is city-specific because new moon times vary by location. Always compute for your city.
Note on Sources
Vedic astronomical basis and traditional Panchang practice
The rule for identifying Adhika Masa is based on Vedic astronomical observation: the relationship between lunar months (new moon to new moon) and solar sign changes (Sun's entry into zodiac signs). This is not a regional or cultural preference—it's how the celestial mechanics work, as understood in the Vedic calendar system.
Traditional Panchang makers use this same rule, though implementation details (like ayanansh calculations and rounding methods) can cause minor variations between different panchangs. The core principle remains: no solar sign change between two new moons = Adhika month. This is the method followed by classical Vedic almanac compilers.
For accurate calculations, use location-aware tools that account for your city's longitude and timezone. Check your city-wise Panchang or tools that show lunar month names and solar sign changes for your specific location.
Note: This guide offers traditional Vedic Panchang timing guidance based on astronomical calculations. It does not replace medical, legal, or financial counsel. Practices vary by region and family tradition—consult your local Panchang and family elders for guidance specific to your situation.