Calendar Facts Finder
Pick a date to see the day of the week, week number, quarter, and whether its year is a leap year.
About the Calendar Facts Finder
Calendar Facts Finder answers common date questions: is a year a leap year, which weekday a date falls on, and which ISO week number it belongs to. It also helps with planning, history questions and spreadsheets or software that use week numbers.
A year is a leap year if it is divisible by 4, except century years, which must be divisible by 400. So 2000 was a leap year but 1900 was not. ISO weeks start on Monday, and week 1 is the week containing the first Thursday of the year, so the first days of January can belong to the last week of the previous year.
How to use it
- Enter a year to check leap status.
- Enter a full date to see its weekday and ISO week.
- Read the results, including the day of the year.
- Try other dates to compare.
Tips and good to know
- Week numbering differs between countries; ISO is common in Europe and business software.
- The Gregorian calendar was adopted at different times, so historical dates before adoption may differ from local records.
- Use Date Difference to count days between two dates.
Frequently asked questions
Is 2100 a leap year?
No, because it is a century year not divisible by 400.
Why is 30 December sometimes in week 1?
ISO weeks can span year boundaries.
Does it handle old dates?
It uses the proleptic Gregorian calendar.