Understand week numbers and plan dates with confidence

Which week-year does a date belong to? Which print layout suits your plans? What does an empty holiday list mean? This guide explains how to use our calendar and interpret its results.

Week-year versus calendar year

An ISO week runs from Monday to Sunday. Week 1 contains January 4 and the first Thursday of the year. A calendar year always starts on January 1, so early January can still belong to the previous week-year. For example, January 1, 2027 falls in week 53 of 2026; week 1 of 2027 starts on January 4. When arranging a delivery, specify the week-year and preferably the actual date range instead of just saying “week 1”.

Check a particular date

Choose a date in the home-page calculator to see its week number and week-year. December 31, 2025 belongs to week 1 of 2026. Consequently, the 2026 week table starts on December 29, 2025. This is not a duplicated week: all seven days stay together in one ISO week. We use the same week convention in every language. Changing the language does not switch to a different national week-numbering system.

Open the calculator example

Print a calendar that fits your purpose

Choose a year and open the printable calendar. One page displays twelve small months; two pages show six months each. Four, six or twelve pages provide larger day cells. Enable writing space for handwritten plans. Check paper size, scale and margins in print preview. Browser-added URLs, dates and page titles can be disabled using the browser’s headers and footers setting. The logo and website address built into our template remain visible.

Interpret holidays and school breaks

Select the country, then the region and, where offered, locality or school group. A regional holiday is not necessarily a day off elsewhere. European entries come from OpenHolidays; coverage varies by country, region and year. An empty list means no matching entries were supplied, not proof that there are no holidays or school breaks. Confirm important dates with the school or responsible authority. For the USA we show federal holidays and observed dates, not a complete set of state holidays or any school holidays.

A retrieval date is not official verification

The retrieval date records when our server downloaded the source. It does not certify that dates are complete or officially approved. If retrieval fails, the site may display clearly labelled cached data. Calculated longer breaks combine weekends with full-day public holidays; they do not include your personal work schedule and do not guarantee days off. We calculate week numbers ourselves and obtain holiday entries from the named source.

Sources and corrections

The links lead to the ISO overview, European data sources and US federal holidays. To report a mistake by email, please include the date, country, region and, if possible, an official source.

Editorial update: October 10, 2026