“Old Christmas” is really December 25 but reckoned on the Julian calendar, the calendar used by the ancient Church and still in use today by some Eastern Churches. Today, Old Calendar Christmas falls on January 7; the difference grows by another day every 130 years. Since this carol is very old it stems from a time when the churches of the British Isles had not yet adopted the Gregorian calendar. It's quite possible that there are versions of The Cherry Tree Carol in which the date of Christmas ranges anywhere from January 4 to January 7, depending on when they were written down.

The most common date in the carol is January 6 and this causes some people to equate the date with the Feast of the Epiphany which is celebrated on January 6. Old Calendar Epiphany is also on January 6 which falls on January 20 in the Gregorian Calendar. The reference in the carol, however, refers to Christmas and not to Epiphany.

      - Mark