How it's calculated
days left = target December date − start date
Counts whole days from the start date to the chosen December date (Dec 1, Dec 25, or Dec 31); rolls to next year if the date has passed. % of year = days ÷ 365 (or 366 in a leap year).
Common questions
What happens once December arrives?
The counter rolls over to December of the following year automatically, so it always points at the next December.
Does it count to the first or the last of December?
It shows several targets at once, including December 1, December 25, and December 31, so you can use whichever you need.