Reference facts for a whole year
How many days, how many weekdays, how many business days, how many ISO weeks, whether it is a leap year, and how much of it is left. These are the least fashionable pages on the site and the most useful: they are the numbers behind a capacity plan, a daily rate, an accrual and a year-end deadline.
The one that repays reading is the week count. A year is 52 weeks in the loose sense, 52 weeks and one day exactly — two in a leap year — and either 52 or 53 ISO weeks depending on the weekday it starts on. A year has 53 ISO weeks when it starts on a Thursday, or when it is a leap year starting on a Wednesday. 2026 starts on a Thursday, so it has 53, and the first days of January 2026 belong to week 1 rather than to the last week of 2025.
"How many are left" has more than one answer
The three countdown pages state their convention rather than assuming it: they count whole remaining days and they do not count today, on the grounds that most of today has gone by the time anyone asks. Add one if your rule counts today. They also give the number of remaining working days, which is the figure that matters for anything with a year-end deadline and the one most counters leave out.