Similar to other Asian lunar calendars, the Mongol year has followed a lunar calendar with a 12-year animal cycle since ancient times. The New Year symbolizes the coming of spring and the re-awakening of nature. The term 'White Moon' is said to refer to dairy products such as milk, which become more plentiful again with the return of Spring.
Preparations for the festival will begin in the month before Tsgaan Sar, with plenty of dumplings made ahead of time and new clothes made or bought.The festivities start on 'Bituun', the day before Tsagaan Sar. On the Bituun day, people thoroughly clean around home, herders also clean the livestock barns and shades, to meet the New Year fresh. The Bituun ceremony also includes burning candles to symbolize enlightenment of the samsara and all sentient beings and putting three pieces of ice at the doorway so that the horse of the deity Palen Lhamo ( the wrathful deity considered to be the principal protectress of Tibet) could drink as the deity is believed to visit every household on this day.
In the morning, it is custom to rise early to greet the dawn of the new year. After the sun has risen, to ensure good health and happiness in the coming year, everyone must take "their first steps of the year". The direction of the steps everyone has to take depends on which lunar year you were born in. Traditionally, Mongolians settle all issues and repay all debts from the old year by this day
When greeting their elders during the White Moon festival, Mongols perform the zolgokh greeting, grasping them by their elbows to show support for them. The eldest receives greetings from each member of the family except for his/her spouse. During the greeting ceremony, family members hold long, typically blue, silk cloths called a khadag. After the ceremony, the extended family eats sheep's tail, mutton, rice with curds, dairy products, buuz, khorkhog. It is also typical to drink airag and exchange gifts.
According to en.wikipedia and officeholidays