The Twelve Days of Christmas are the festive days beginning Christmas Day (25 December). This period is also known as Christmastide and Twelvetide.
Unfortunately,because there a drive to start the “christmas selling period” there is a misunderstanding that Christmas ends promptly on Christmas Day. That is 100% wrong.
The Twelfth Night of Christmas is always on the evening of 5 January, but the Twelfth Day can either precede or follow the Twelfth Night according to which Christian tradition is followed. Twelfth Night is followed by the Feast of the Epiphany on 6 January. In some traditions, the first day of Epiphany (6 January) and the twelfth day of Christmas overlap.
Over the centuries, differing churches and sects of Christianity have changed the actual traditions, time frame and their interpretations. St. Stephen’s Day (or Boxing Day), for example, is 26 December in the Western Church and 27 December in the Eastern Church. Boxing Day, the first weekday after Christmas, is observed as a legal holiday in parts of the Commonwealth of Nations. 28 December is Childermas or the Feast of the Innocents. Currently, the twelve days and nights are celebrated in widely varying ways around the world. For example, some give gifts only on Christmas Day, some only on Twelfth Night, and some each of the twelve nights.
So enjoy the season!