Short answers, pulled from the story.
The true origin of Boxing Day lies in the humble alms box placed in the narthex of Christian churches during the Middle Ages. On the 26th of December, the Feast of Saint Stephen, these boxes were opened to distribute collected donations to the poor, a tradition that dates back to the late Roman and early Christian eras.
If Christmas Day is a Sunday, the Boxing Day holiday is still observed on the 26th of December, with the substitute holiday for Christmas Day observed on the 27th of December. The Banking and Financial Dealings Act 1971 later regulated these bank holidays, stating that the 26th of December would be observed as a bank holiday if it were not a Sunday.
In Australia, the holiday is a public holiday in all jurisdictions except South Australia, where Proclamation Day is celebrated on the first weekday after Christmas Day. In Canada, Boxing Day is a federal statutory holiday for federally regulated industries and a recognized holiday in Ontario, though in New Brunswick, it is listed as a prescribed day of rest rather than a paid public holiday.
The rise of Black Friday sales in the late 2000s and 2010s has significantly impacted traditional Boxing Day sales, particularly in Canada and the UK. In 2019, a retail analysis firm estimated a 9.8% drop in British store traffic on Boxing Day compared to 2018, the largest year-over-year drop since 2010, citing factors such as the weather, the growing prominence of online shopping, and the increasing influence of Black Friday.
In the United Kingdom, the Home Nations' major football leagues hold a full programme of fixtures on the 26th of December, originally designed to avoid long-distance travel for away games. The Australian cricket team has traditionally opened one of its test matches on Boxing Day at the Melbourne Cricket Ground, a practice formalized by the Australian Cricket Board in 1980.
In the United Kingdom, the culinary tradition of Boxing Day centers on the consumption of leftovers from the previous day's Christmas dinner, with turkey often repurposed into sandwiches or curries. This practice reflects a practical approach to the holiday, allowing families to enjoy the remnants of the festive feast without the need for additional cooking.