Thadingyut is the seventh month of the traditional Burmese calendar. As a custom, it is held at the end of the Buddhist sabbath (Vassa) and is the second most popular festival in Myanmar after Thingyan Festival (New Year Water Festival). Thadingyut festival lasts for three days: the day before the full moon day, the full moon day (when Buddha descends from heaven) and the day after the full moon day.
Buddhists celebrate Thadingyut to welcome the Buddha and his disciples by enlightening and festooning the streets, houses and public buildings with colored electric bulbs or candles, which represent those three stairways.
On the 3 days of the festival, Buddhist devotees will light and decorate streets, houses, and public buildings with electric light bulbs or colored candles, representing the three stairs (gold, silver and ruby) that all the saints and evils did so that Buddha could return from Trayastrimsa Paradise.
During Thadingyut Festival, there are zat pwes (Myanmar musical plays), free movie shows and stage shows on most of the streets around the country. There are also a lot of food stalls, which sell a variety of Myanmar traditional foods and shops, which sell toys, kitchen utensils, and other useful stuff on most of the streets. Sometime people just walk around in those streets just for sightseeing and have fun. Some people like to play with firecrackers and fire balloons.
During the festival days, Buddhists usually go to pagodas and monasteries to pay homage to Triple Gems, paying respect to the monks and offer foods. And some Buddhists usually fast on the full moon day. Young people usually pay respect (gadaw) to their parents, teachers, and elderly relative and offer them some fruits and other gifts. Also while paying homage the younger people usually ask for forgiveness from the wrong-doings they have caused upon their parents or the other elderly relatives throughout the year. Traditionally the elders tell their youngsters that they forgive any of their wrongdoings and continue to bless them with good luck and gift some big notes as pocket money. It is also usual for younger siblings to pay homage to their older siblings. In return, the elder ones wish good luck for them and give them some pocket money.
In addition to the usual activities, many places will have different traditions, such as Dawei locals holding thabeik hmyaw pwe, in which alms bowls filled with offertories (e.g., flowers, water, oil lamps, candles and joss-sticks) are set adrift at sea to Shin Upagutta; or Shwegyin locals hold a mi hmyaw pwe festival in which colorful oil lanterns are set adrift into the Shwegyin River to Shin Upagutta.
According to Wikipedia