There is a russian old tradition - Old New Year!
Many years ago there was an Julian Calendar in Russia, the new Gregorian Calendar was started only on 14 February 1918.
As I see in Wiki the Gregorian calendar replaced the Julian in Catholic countries beginning in 1582.
Old Style (O.S.) and New Style (N.S.) has been used only for some Holidays like New Year. Even today almost 100 years after calendars replacement we still celebrate 2 New Years.