As the Russian Orthodox Church follows the Julian calendar, many Russian Orthodox holidays fall 12 days later than Western Christian holidays.
Therefore Russians have the opportunity to celebrate the New Year twice. The main celebration is on December 31st. The second time is on January 13th. Gift giving is not obligatory for this day. People wear masks and funny costumes, wander around, sing carols, gather for a big meal. Children go in costumes from house to house for the second time in the new year.
A New Year tree is kept until January 14th and sometimes longer - until Epiphany (January 19th.)