Gregorian calendar, New Style calendar - the solar calendar now in general use, introduced by Gregory XIII in 1582 to correct an error in the Julian calendar by suppressing 10 days, making Oct 5 be called Oct 15, and providing that only centenary years divisible by 400 should be leap years; it was adopted by Great Britain and the American colonies in 1752

December 31, New Year's Eve - the last day of the year

Christmas Day, Dec 25, Xmas, Christmas - a Christian holiday celebrating the birth of Christ; a quarter day in England, Wales, and Ireland

Christmas, Christmastide, Christmastime, Noel, Yule, Yuletide - period extending from Dec. 24 to Jan. 6

Gregorian calendar month - a month in the Gregorian calendar

mid-December - the middle part of December

winter, wintertime - the coldest season of the year; in the northern hemisphere it extends from the winter solstice to the vernal equinox