Yadayar is a custom of Burmese people, done to promote one’s luck. Originally a belief of Indian Hindi Brahmans , it has established itself as a Burmese custom, even incorporated into Buddhist belief of Myanmar people (although it is a total contradiction to the teachings of Lord Buddha). It is a concept which has no equivalence in the western culture, and one difficult to explain to foreigners. Simply speaking, it is an act which is totally unconnected to the outcome you wish for, but which, in celestial meanings, has great influence over the expected outcome. For example, suppose you wish to sell your old car which you find difficult to attract any interested person, you go and ask for the advice from an astrologer. He will, base on his astrological calculations, which usually takes into consideration of the day you were born, provides you a yadayar. This yadayar might be a simple thing like hitting your car with a certain number of, say 7 roses, roses, or a complex task like hitting the car with the number of roses equivalent to your age, pouring coconut water over the car 7 times, all of which has to be done exactly at 7:30 AM on the day of the week you were born. Some of the yadayars might even be more complex than this. Yes, it is ridiculous as it sounds, many many Burmese strongly believe in such unexplained and celestial concept (including my mother)!
This is just an example of yadayar. Nowadays, in order to hide the Brahman origin, many astrologers will give a yadayar in a form of merit making; this might be releasing a certain number of captive birds (which you can easily purchased from vendors around the pagodas), or donating a certain number of a flower or leaf at a particular pagoda (e.g. Shwedagon Pagoda), done at the certain time and date. In this way, Indian Brahman belief of yadayar is successfully incorporated into the Buddhist belief of merit making. Many Burmese Buddhists actually believe that the concept of yadayar is in accordance with the teachings of Lord Buddha (which is not). However, the custom of yadayar is so firmly rooted in the Myanmar belief that it has become a custom of Myanmar people.