Most of Russians are Orthodox Christians, and celebrate Christmas (Рождество́) on January 7th (according to the Gregorian calendar). In Kievan Rus, Christmas became an official holiday after the baptism of Prince Vladimir in the late 10th century. However, considering that the Christian community existed in ancient Kiev even earlier, the celebration may date back further.
During the Soviet period of the 1920s, religious holidays were rooted out by the atheist government. The Christmas tree and celebrations associated with it gradually lost their meaning. However, in 1935, after an unexpected twist in government policy, Christmas traditions were accepted as part of the secular holiday of New Year. Ever since then, the "Christmas" tree in Russia has persistently been perceived as a "New Year" tree. Presents and a visit from Father Frost also became part of New Year traditions, losing their associations with Christmas.
Only in 1991, after the collapse of the Soviet Union, the tradition of celebrating Christmas was restored. Since 1992, Christmas has become a national holiday in Russia, as part of the ten-day holiday at the start of every new year.
Nowadays, many Russians openly observe Christmas by attending all-night church services and getting together with their families for a special Christmas meal. However, unlike Western Europeans and Americans, Russians see Christmas primarily as a religious holiday that doesn't have any secular traditions associated with it.
По материалам: RBTH: 10 facts about Orthodox Christmas