what is the meaning of old christmas?

Answer 1

This is all due to the switch over from the Julian calendar to the Gregorian calendar (which we use now).

England lagged a long way behind Catholic Europe in adoting the "new" Gregorian calendar and didn't move across until the middle of the 18th century. By this time England was, in effect, 11 days out of step with the continent.

Before the calendar was reformed, England celebrated Christmas on the equivalent of the 6th of January by our modern, Gregorian reckoning. That is why in some parts of Great Britain people still call the 6th of January, Old Christmas Day.