For most of us Christmas is over but for members of the Russian Orthodox Church, Christmas Day is in January.
The calendar was introduced more than 1,000 years ago by Julius Caesar. Hundreds of years passed and Pope Gregory believed it was inaccurate and so he changed it.
Many churches went on to adopt the new calender, but the Russian Orthodox Church still celebrates Christmas and other festivals on the old dates 13 days later.
Press Packer Sophie wishes everyone a Merry Christmas!
"I am half Russian and I live in Oxford. I am a member of the Russian Orthodox Church, so for me Monday the 7 January is my Christmas day.
We prepare for Christmas by not eating meat. We have to fast. For us, Advent started just before December but it goes on for longer than other people's.
On Christmas day itself we go to church and celebrate. Afterwards we greet one another with 'Merry Christmas'.
Longer to buy presents
Most people go home after church and open their Christmas presents. It's quite a bonus having Christmas later than other people because you get longer to buy gifts!
Christmas is very exciting for me and is one of my favourite feast days.
I go to a Roman Catholic school so we're always doing Christmassy things in December. Sometimes people ask me why I'm not feeling Christmassy and I have to tell them over and over again we don't celebrate Christmas on the 25th.
I will go back to school on Tuesday which, for me, will be one day after Christmas.
I wish you all a Merry Christmas!
Sophie, 10, Oxford, England
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