Calendar by Month and Year

What this calendar shows

Pick a month and a year and the page lays that month out week by week: every date under its weekday (the grid starts on Sunday), weekends in red and a ring around each holiday; under the grid, the number of days, the day-of-year span, the ISO 8601 weeks the month spans and the list of holidays with their dates. The "Year" option in the month list gathers the whole year into twelve compact grids, each one linking to its own month page.

The rule the grid is built on

Month lengths are fixed by the calendar itself, and February depends on whether the year is a leap year. The Gregorian rule is:

That is why 2024 and 2028 are leap years, 2100 will not be, and 2000 was. The rule comes from the 1582 reform under Gregory XIII: the Julian year ran about 11 minutes longer than the astronomical one, and over sixteen centuries ten spare days had piled up. Dropping three leap years in every four hundred is what cancels the drift.

Week numbers follow ISO 8601: a week runs Monday to Sunday, and week 1 of a year is the one that contains its first Thursday.

Limits and caveats

• The calendar is Gregorian and starts at 1583. For earlier dates a Gregorian weekday is a back-projection that disagrees with the historical record, so those pages do not exist here.
• Week numbers are ISO 8601. The US convention, which calls the week containing January 1 week 1, gives different numbers and is not shown.
• The holiday list covers 2025 onwards, so pages up to 2024 mark none. The dates come from the same registry as the "When is" pages, so the two cannot disagree.
• Those are international, religious and US federal holidays; national public-holiday calendars of other countries are not included.
• We do not publish a PDF version of this calendar — the page is meant to be read in the browser.

The 2026 calendar month by month