December 2025 Calendar: The Cold Moon and the Solstice
December 2025 closed the year from a Monday start, and the moon took the high road. The full Cold Moon on Thursday, December 4 was the year's highest-riding full moon; no other in 2025 arced taller. Behind it came a 31-day month of 23 business days, five Mondays, Tuesdays and Wednesdays. The grid ended, correctly and a little oddly, inside week 1 of 2026.
The shape of December 2025
December opened on Monday, December 1 and closed on Wednesday, December 31. The count ran to five Mondays, five Tuesdays and five Wednesdays, against four of each other weekday. That left 23 business days and eight weekend days across weeks 49, 50, 51, 52 and 1.
Yes, week 1. The month's final days sat in the first calendar week of 2026. The year 2026 began early in the grid's top corner. The page is not broken; week numbering simply works that way.
Cold moon, darkest night, solstice
The Cold Moon on December 4 rode the highest arc of any full moon in 2025. December full moons climb steeply and linger. The last quarter arrived on December 11.
The new moon on December 20 brought the year's darkest night. The solstice arrived the next day, Sunday, December 21. It was the year's shortest day in the northern half of the world and longest in the southern. A first-quarter moon on December 27 closed the set.
A hard opening week, then a busy month
The month opened with tragedy. Monsoon flooding and landslides killed more than 1,100 people across Indonesia, Sri Lanka, Malaysia and Thailand in the first week. Sumatra and northern Sri Lanka were hit hardest.
A magnitude-7.6 earthquake struck off northern Japan's Aomori prefecture on December 8. It injured dozens and sent tsunami waves of up to 70 cm along the coast.
December 5 brought two big announcements. Netflix agreed to buy Warner Bros.' film and TV studios plus HBO Max in a 72-billion-dollar deal. Washington's Kennedy Center hosted the first draw for the 48-team World Cup that same day.
It set twelve groups for the tournament the United States, Canada and Mexico host in 2026. Lionel Messi's Inter Miami won their first MLS Cup on December 6, beating the Vancouver Whitecaps 3-1 in Fort Lauderdale.
The 2025 Nobel Peace Prize was presented in Oslo on December 10 to Venezuela's Maria Corina Machado. Her daughter accepted it as Machado emerged from hiding. The same day, Australia's world-first under-16 social media ban took effect, forcing platforms to deactivate minors' accounts.
Screens big and small close the year
Avatar: Fire and Ash, the third Pandora epic, opened worldwide on December 19. It topped the month with roughly $345 million in its first weekend. Clair Obscur: Expedition 33 won Game of the Year at The Game Awards on December 11. It took a record nine awards in total.
Stranger Things ended its five-season run on December 31 with a roughly two-hour finale. Simulcast screenings put it in movie theaters as well. The year's last night belonged to Hawkins.
The Cold Moon took the year's highest arc, and the grid took an early peek at 2026. Both ran on time.