Buddha Purnima – Buddhists remembering threefold events, the birth of The Buddha in Lumbini, attainment of Buddhahood in Buddhagaya and his Parinirvana in Kusinara celebrate Buddha Purnima – Vesak which falls on full moon of May. Devotees go to religious places on this day freely as it is official holiday. Practising generosity, cultivating morality and contemplating on meditation is done in every Buddhist temples. Going to Swayambhu, displaying picture of Buddha outside the house, reciting devotional songs and Buddha’s relic procession are some of colourful events take in Nepal during this day .
Gunla – Religious month in August when Buddhists visits Swayambhu daily for this month. It is considered as religious month. Playing Gunla drums, which is religious music, devotees visit Swayambhu and Buddhist shrines (Vaidya, which is displayed specially during this month in Baha and Bahis in Kathmandu Valley).
Vijaya dasami – Buddhists commemorate this day as a day of victory of peace. Emperor Asoka, who lived 2 century after the Buddha gave up weapon and known as Dhammasoka from Chandasoka. By listening to the novice monk the warrior Emperor Asoka became peaceful in his heart. After becoming devout to Buddhism he built shrines and pagodas across the India and Nepal. Thanks to his thoughtful action, stabilising pillars and rocks, today we know where the Buddha lived and taught the Dharma.
Mukha Astami – Annually during month of October-November at Pasupati, god Siva is covered by The Buddha’s face and done rituals. For this day Pasupati becomes a Buddhist shrine. During this period Buddhists observe precepts (vrata) and participate in rituals.
Chaita Dasain – In the month of December-January Statue of Compassion (Janmadya, Karunamaya) is put in chariot taking in parade around the Kathmandu city. Fortnight before the Karunamaya is given bath, redrawn face. City parade with national troop takes a week. During this week chariot is stopped over night on the way to the Shrine where devotees visit and lit lamps and do offerings.
Panjaran – Give alms to shrines and Gurju (household Buddhist monks) in Swayambhu and in household. Panjaran Bigu is time when devotees offer various foods to Gurjus.
(Article Source: http://www.lumbini.org.uk/festivals.html)