Well... actually January 7 will be Orthodox Christmas. The Orthodox Church never accepted the Gregorian calendar. There was a move, in the 1920s, to adopt a revised Julian calendar but only some Orthodox Churches have adopted it.
The discrepancy between the Julian and Gregorian calendars has now grown to the point were January 7 will be December 25 under the old system -- thus, Orthodox Christmas.
We don't know why Monday has been designated Old Rock Day. If Old Rock Day had been scheduled for January 4, we might have supposed it was a poke-in-the-eye salute to Anglican Bishop James Ussher, who was born on January 4, 1581.
Bishop Ussher would not have celebrated Old Rock Day. He didn't think any rocks were particularly old. He's the fellow who calculated that the world was created by God on the night preceding October 23, 4004 B.C.
Monday will also be Harlem Globetrotters Day. The Harlem Globetrotters played their first game on January 7, 1927. But they didn't play that game in Harlem. Actually, the Globetrotters were formed on the South Side of Chicago; according to Wikipedia, the Globetrotters didn't play their first 'home' game in Harlem until 1968.