Why does 2020 have 53 ISO weeks?
2020 is a leap year and January 1, 2020 was a Wednesday — the one other condition, besides Jan 1 being a Thursday, that adds a 53rd week.
Worked from a fixed input so the numbers stay put: 2020. Try your own on the home page.
ISO year 2020 has 53 weeks. (2020 is a leap year and January 1 is a Wednesday.)
- ISO year
- 2020
- Weeks in that ISO year
- 53
Other examples
Not a general calendar or scheduling tool, and it does not know about business fiscal-year or retail 4-4-5 week numbering, which are different systems that also call themselves "week numbers." It has no concept of time of day or timezone — it operates on calendar dates only. Not for US-style "week of the month" or non-ISO week-start conventions (e.g. Sunday-start week numbering used by some US calendars).