Tsagaan Sar festival corresponds to the Mongol New Year (between the end of January and early March, depending on the position of the moon). Celebrations for the new spring in February, although a little early, coincides with the celebrations for the New Year of the lunar calendar. A calendar supposedly invented by Central Asian tribes, which corresponds, in Mongolia, to a 12 year century, a twelve month year and a twelve hour day. According to Tibetan-Mongol cosmology, the world would be the result of the interactivity between five elements - iron, earth, fire, water and wood - each materialized by a colour. Tsagaan Sar can be translated by "the month of white" and it is also the time when milk is collected again. According to the ritual, the preparations start a month in advance. The families prepare the presents, clean inside the ghers and buy new clothes. According to the tradition, the fastest sheep should be slaughtered, so as to serve its saddle and boiled tail, during the whole time of the celebrations, since Tsagaan Sar symbolizes the family's prosperity. Before dawn, the nomads get out of the yurt and bow to the four cardinal points, before performing the offerings of mare or cow's milk. Then comes a whole series of family greetings, in a well-established order. At day break, they share New Year's tea, before going out to greet relatives or important personalities, to whom they offer presents. The mutton can then be carved and shared, as well as the dairies. In town, the celebrations last one day only, whereas out in the steppe, they go on for a week or two.