1. On December 29, 1845, the Boston Evening Transcript published an article reporting on the discovery of the planet Neptune by German astronomer Johann Gottfried Galle. The discovery was made possible by calculations made by French mathematician Urbain Le Verrier, who predicted the existence and location of Neptune based on its gravitational influence on other planets.

2. In 1890, the Massachusetts Institute of Technology (MIT) held its first winter carnival on December 29. The event featured ice skating, snowshoeing, and other winter sports, as well as a torchlight parade and a fireworks display. The winter carnival has remained a tradition at MIT, and is now known as the MIT Ski & Board Club Winter Carnival.

3. On December 29, 1975, an all-time record low temperature of -35 degrees Fahrenheit was recorded in Chester, Massachusetts. The extreme cold was due to a polar vortex that had descended over the eastern United States, bringing with it bitter arctic air.

4. In 2003, Massachusetts became the first state in the United States to legalize same-sex marriage. On December 29 of that year, the Massachusetts Supreme Judicial Court issued a ruling in Goodridge v. Department of Public Health, declaring that the state's ban on same-sex marriage violated the Massachusetts Constitution's equal protection clause.

5. On December 29, 2015, the city of Boston hosted its first ever outdoor professional hockey game, the 2016 NHL Winter Classic, at Gillette Stadium in nearby Foxborough. The game featured the Boston Bruins and the Montreal Canadiens, and drew over 67,000 fans. The Winter Classic has since become an annual event, showcasing outdoor hockey games in unique venues around the United States.