A Legacy Etched in Time
Nepal Sambat (NS) is more than a calendar, it is a symbolic thread connecting past, present, and future in Nepal’s cultural tapestry. Established on October 20, 879 AD during the reign of King Raghavadeva, it marked the commencement of a unique era rooted in lunar and solar harmony.
Unlike most calendars named after rulers or religious epochs, Nepal Sambat draws its name from the land itself. Over centuries, its dates were inscribed on coins, stone tablets, royal decrees, manuscripts, and sacred texts anchoring it as the official calendar through the Thakuri and Malla periods.
Central to its founding legend is Sankhadhar Sakhwa, a figure revered in folklore for liberating the people from debt - an act celebrated as the genesis of Nepal Sambat.
Over time, with political shifts and calendar reforms, Nepal Sambat gradually lost its status as the national calendar. In 1769, following the fall of the Malla dynasty, the Gorkha rulers introduced other calendar systems, officially replacing NS. Yet despite this, the calendar remained alive in cultural practice, especially among the Newar community, used to guide festivals, life-cycle rituals, and community observances.
Even though many official uses waned, inscriptions and documents continued to preserve Nepal Sambat’s dates, ensuring its traces remained visible to scholars and cultural custodians.
The Structure and Principle Behind NS
Nepal Sambat is a lunisolar calendar: months are tied to the moon’s phases yet adjusted to stay in sync with the solar year. Each lunar month may have 29 or 30 days, and periodic corrections ensure alignment with seasonal cycles.
In historical records, early inscriptions are dated in NS, and the name "Nepal vatsara" appears as early as NS 148 (AD 1028), indicating the calendar was in active use by then. Later chronicles tie its origin to religious or astronomical events, such as dedications to Pashupati (Lord Shiva) near the national shrine of Pashupatinath, but its exact genesis remains debated among scholarship.
Though many technical manuscripts were lost or remained hidden, the surviving documents provided clues for modern reconstruction of its logic.
A New Beginning in the Digital Age
By 2017, Spiralogics began charting a path to revive Nepal Sambat, not just as a static record but as a fully-fledged digital calendar system. The initial step involved manually capturing existing calendrical data. But quickly, the team realized that a long-term solution would require automated calculation, not manual maintenance.
Under the leadership of Mr. Saunak Ranjitkar, Spiralogics delved into the astronomical foundations of NS, and discovered that the motions of the moon around Earth, combined with the positional relationships of the sun, moon, and planets, could be modeled to compute Nepal Sambat dates with precision. This insight gave birth to a unique algorithm capable of generating all the elements of the calendar dates, tithis, conversions, and more for any day in the past or future.
Explore the full technical model in our whitepaper, which presents the mathematical derivation, validation, and application of the algorithm.
Watch the SkillUp session with Saunak Ranjitkar, where he explains how centuries-old celestial patterns became a modern digital system.
With the algorithm in place, Spiralogics built the Nepal Sambat Mobile App. Today, the app empowers users to explore:
- Tithi (Nepal Sambat month and lunar date)
- Sunrise, Sunset, Moonrise, Moonset
- Sunsign, Moonsign, Nakshatra
- Festival listings by month/year
- Date conversion between NS, Bikram Sambat, and Gregorian (AD)
The app was officially launched on November 5, 2021 (Kachhalatho 1, NS 1142), marking the moment when the ancient calendar found a new home in the digital era.
Toward a Living Calendar for Future Generations
Nepal Sambat’s revival is a compelling example of how cultural heritage and technology can unite. What was once preserved in stone, manuscripts, and oral tradition is now accessible to anyone with a smartphone.
By reconstructing the astronomical logic and embedding it into a robust algorithm, Spiralogics ensures that Nepal Sambat can evolve, endure, and adapt not as a relic, but as a living, usable calendar.
