Why Do Some People Celebrate Christmas On 7th January?

The Eastern Orthodox Church celebrate Christmas day on 7th January. The Eastern Orthodox church is the second largest, Christian institution in the world if protestantism as an entity is excluded.
The Orthodox Churc uses the old Julain calender which is 13 days behind the Gregorian calender.
In the former Soviet Republic the Bolsheviks adopted the Gregorian calender at the end of 1917 which put them in line with the rest of the Western world. However the Orthodox church who were opposed to the oppressive steps taken by the Bolsheviks to supress religion, kept the Julian calender.
In communist countries organised religion was repressed and pushed underground although it was never stamped out.
For many people in communist and former communist states religious holidays and festivals became just holidays and Christmas was regarded as many as just a holiday on January 7th.
However Russian politians do now attend church at Christmas and many people again celebrate Christams as a religious festival in Russia. The members of the Eastern Church have their traditions firmly embedded in the Julian calender.