Wikipedia
Bachhalā ( Nepal Bhasa: बछला) is the seventh month in the Nepal Era calendar, the national lunar calendar of Nepal. The month coincides with Vaisakha in the Hindu lunar calendar and May in the Gregorian calendar.
Bachhalā begins with the new moon and the full moon falls on the 15th of the lunar month. The month is divided into the bright and dark fortnights which are known as Bachhalā Thwa and Bachhalā Gā respectively.
Among the most important festivals of the month, Bunga Dyah Jatra, the chariot pulling festival of the Buddhist deity Red Avalokiteśvara, begins at Patan on the 4th day of the bright fortnight.
The full moon day of Baisākh Purnimā is one of the year's most widely celebrated holidays. It is known as Swānyā Punhi in Nepal Bhasa and means "Full Moon Day of Flowers". The holiday celebrates three events in the Buddha's life—his birth, enlightenment and Nirvana.