This day is celebrated to mark the birthday of the Lord Buddha which dates back in about 543 BC. It falls on Jestha Purnima (Full moon night-May/June).
The festival of "Gai Jatra" (the procession of cows) which is one of the most popular festivals, is generally celebrated in the Nepalese month of Bhadra (August-September). This festival has its roots in the belief that the god of death, Yamaraj, must be feared and hence worshipped
Dashain (Bijaya Dashami)
During the month of Kartik in the Bikram Sambat calendar (late September and early October), the Nepalese people indulge in the biggest festival of the year, Dashain. Dashain is the longest and the most auspicious festival in the Nepalese annual calendar, celebrated by Nepalese of all caste and creed throughout the country. The fifteen days of celebration occurs during the bright lunar fortnight ending on the day of the full moon.
Tihar, the festival of lights is one of the most dazzling of all Hindu festivals. In this festival we worship Goddess Laxmi, the Goddess of wealth. It heralds the month of Kartik (October/November) starting with Kukur Puja-Narak Chaturdashi.
This festival falls in mid Magh (January/February). It is celebrated as the birthday of Saraswati, the Goddess of Learning. She is the lily-white daughter of Shiva and Durga in spotless white robe and seated in a full-blown lotus. This day is also dedicated to the martyrs of Nepal and hence celebrated as Martyr's Day.
Fagu Purnima (Holi)
The ancient Hindu festival of Holi falls on late February or on early March. Allegedly named after the mythical demon Holika, it is a day when the feast of colors is celebrated. The festival is of a week. However, it's only the last day that is observed by all with colors
Lhosar is the Tibetan New Year which falls on February/March. This festival is mast impressively observed by all the Tibetan-speaking populations. They organize folk songs and dances on this occasion. These dances can be seen in Khumbu, Helambu and other northern regions of Nepal and also at Boudhanath in Kathmandu
Shree Krishna Janmastami
Sri Krishna Janmastami marks the celebration of the birth of Lord Sri Krishna. This festival is also known as Krishna Jayanti or Janmashtami. Lord Krishna is regarded as the 8th avatar or 'incarnation' of Lord Vishnu. It falls on Saptami of Bhadra (August/September).
Indrajatra (Holiday Only in Kathmandu)
This festival falls in the end of Bhadra (August/September). Both Hindus and Buddhists unite to celebrate the festival of Indra Jatra with great enthusiasm.
Maha Shiva Ratri
This day is the celebration dedicated to the Lord Shiva which falls on the Trayodashi of the month Fagun (February/March). So many devotees are willing to worship in very much popular Hindus Temple Pashupatinath in Kathmandu. Every Year Thousands of Devotees arrive in Kathmandu for this Festival to celebrate & worship.
Ghode Jatra, the Horse Racing Day falls on Darhsa Shrad Aunsi of the month Chaitra (March/April). A grand horse parade takes place at Tundikhel, the central point of the city reputed to have been in the former days the largest parade ground in Asia.
Rato Macchendranath Jatra
(Begins on the full moon day of Baisakh) This is the longest as well as the most important festival of Patan. It begins with several days of ceremonies and the fabrication of a wooden-wheeled chariot at Pulchowk, near the Ashoka Stupa.