Nepal runs on the Bikram Sambat calendar, which is roughly 56 years and 8 months ahead of the Gregorian one and starts its year in mid-April. Its months, Baisakh through Chaitra, are solar, but the festivals inside them are fixed by tithi, a lunar day. A tithi is the time the moon takes to gain twelve degrees on the sun, which is not a fixed number of hours, so tithis drift against solar days and festivals drift against the Gregorian calendar by up to several weeks from year to year.
The practical consequence for a visitor is simple. Anyone who tells you that Nepali Mother's Day is on a particular Gregorian date every year is wrong. What is stable is the Nepali month and the tithi: Matatirtha Aunsi is always the new moon of Baisakh, Maha Shivaratri is always the fourteenth of the dark fortnight of Falgun, and the Mahalaxmi Jatra always opens on Kartik Shukla Chaturdashi. Every page in this section gives the tithi first and the Gregorian window second, in that order, deliberately.
Two further wrinkles catch people out. First, some tithis are skipped or repeated in a given lunar month, which is why a festival occasionally appears to jump a day relative to what you expected. Second, the authoritative determination is made by the Nepali panchanga, the astronomical almanac, and published for the year; for a local jatra the temple guthi, the hereditary trust that funds and runs it, confirms the working dates. If a trip depends on being present, ask the temple committee or the municipality directly.






