Why Do Nepali Festival Dates Change Every Year? Tithi and the Lunar Calendar Explained

Every year someone asks: “Why is Dashain in Kartik this year when it was in Asoj last year?” The short answer is that Nepal runs on two calendars at once. The months and dates you see on a patro follow the sun, but most festivals follow the moon. Because the two don’t line up neatly, festivals drift around the solar calendar from year to year.

This guide explains how that works, which festivals move, which ones stay put, and where the official dates come from.

Two calendars on one page

The Bikram Sambat (BS) months, Baisakh to Chaitra, are solar. A new month starts on a sankranti, the day the sun enters a new zodiac sign. That is why Nepali New Year (Baisakh 1) always falls around April 13 or 14, and Maghe Sankranti is always Magh 1. If you want the details, our guide to how the Bikram Sambat calendar works covers it.

Alongside that runs a lunar calendar. Its months follow the moon from one new moon (or full moon) to the next, about 29.5 days. Twelve lunar months make roughly 354 days, about 11 days short of a solar year. So a festival tied to the moon arrives about 11 days earlier each year, until the calendar adds an extra month to catch up.

What is a tithi?

A tithi (तिथि) is a lunar day. Each lunar month has 30 tithis, split into two halves:

• Shukla paksha (शुक्ल पक्ष), the bright half, when the moon grows from new moon to full moon. It ends on Purnima (पूर्णिमा), the full moon.
• Krishna paksha (कृष्ण पक्ष), the dark half, when the moon shrinks. It ends on Aunsi (औंसी), the new moon.

Each tithi is the time it takes the moon to move 12 degrees ahead of the sun. That doesn’t match a 24-hour day exactly, so a tithi can start in the middle of a day. Astrologers decide which tithi “counts” for a date, usually the one in effect at sunrise. Occasionally a tithi is skipped or repeated, which is why a festival can sometimes shift by a day in a way that looks surprising.

How festivals are tied to the moon

Most festivals are defined as “this tithi of this lunar month”. Here are the common ones:

Because the lunar months slide against the solar ones, the same tithi lands on a different BS date each year. Dashain is the famous example: depending on the year, Bijaya Dashami can be in Asoj or well into Kartik.

Why some years have a leap month

If nothing corrected the 11-day gap, festivals would slowly drift through every season. To stop that, the lunar calendar adds an extra month, called adhik maas (अधिक मास) or malmas, roughly every 32 to 33 months. In a year with an adhik maas, festivals after it come about three weeks later than in the year before. That is why the jump between two Dashains can be so large.

Festivals that never move

Some days follow the solar calendar instead, so they keep the same BS date every year:

• Nepali New Year: Baisakh 1
• Maghe Sankranti: Magh 1
• Saune Sankranti: Shrawan 1
• Constitution Day: Asoj 3
• Prithvi Jayanti: Poush 27

These are built into our Nepali calendar, so they always show on the right day.

Who decides the official dates?

In Nepal, the Nepal Panchanga Nirnayak Samiti (the calendar committee) works out the tithis and festival dates for each year and publishes them in the official patro. The government then announces public holidays based on those dates. Different communities may also follow their own traditions, which is why some festivals, like Holi in the hills and the Terai, are celebrated on different days in different places.

Because the dates are calculated each year, we add the year’s lunar festivals to our festival list from the official calendar instead of guessing them with a formula.

See this year’s festivals and holidays

A quick way to remember it

• Solar dates (sankranti, New Year, national days) stay put.
• Lunar festivals (Dashain, Tihar, Holi, Teej, Chhath) move by about 11 days a year, then jump back after a leap month.
• When in doubt, check the official patro for the year.

To find the English date of any festival once you know its Nepali date, use the date converter. And if you want to wish someone well, our greeting card maker makes a Dashain or Tihar card in Nepali in a minute.