The day after Christmas is called Boxing Day in England. December 26th was also known as St. Stephen's Day, after the first Christian martyr. Money was collected in alms-boxes placed in churches during the festive season. This money was then distributed to the poor and needy after Christmas.
Boxing Day was first observed during the Middle Ages. In Jane Austen's time the upper classes presented gifts in boxes to their servants on December 26 for good service the day before and during the previous year. The servants were often given the day off, and if December 26 fell on a Saturday or Sunday, Boxing Day took place on the following Monday. Boxing Day was also a traditional day for fox hunting.
Learn more about Boxing Day on the All About Christmas website.
This Snopes article about Boxing Day and its origins provides a more extensive overview as well: Click here.
To help you understand the Christian Calendar of that era, here is a listing:
Twelfth Night January 5
Epiphany January 6
Plough Monday First Monday after Epiphany
Hilary Term (law courts) Begins in January
Hilary Term (Cambridge) Begins in January
Hilary Term (Oxford) Begins in January
Candlemas February 2
Lady Day (a quarter day) March 25
Easter Term (Oxford)
Easter Term (Cambridge)
Easter In March or April
Easter Term (law courts) Begins after Easter
Ascension 40 days after Easter
Whitsunday (Pentecost) 50 days after Easter
May Day May 1
Midsummer (a quarter day) June 24
Trinity Term (law term) Begins after Whitsunday
Trinity Term (Oxford) Begins in June
Laminas (Loaf Mass) August 1
Michaelmas (a quarter day) September 29
Michaelmas Term Begins in OctoberMichaelmas Term Begins in October
Michaelmas Term Begins in November
All Hallows, All Saints November 1
All Souls November 2
Guy Fawkes Day November 5
Martinmas November 11
Christmas (a quarter day) December 25
Boxing Day Generally, first weekday after Christmas
Click on The Book of Days and then the Calendar of Days to learn more details about these yearly events and how and why they are celebrated.