Date Calculator

Days Between Two Dates

Determine the total years, months, weeks and days separating two dates. Press the "Settings" button to input any holidays you wish to consider.

Add to or Subtract from a Date

History of the Gregorian Calendar

The Gregorian calendar is the dominant system in use today. In this calendar a typical year contains 365 days, while a leap year adds an extra day to February. April, June, September and November each have 30 days; the remaining months have 31 days, except February which holds 28 days in a common year and 29 days in a leap year.

The Gregorian calendar evolved from the Julian calendar, which itself was a refinement of the ancient Roman calendar. The Roman system was thought to be a lunar‐based calendar tracking the moon’s phases. Early Romans allegedly used a ten‑month, 304‑day scheme, leaving roughly fifty days as an unscheduled winter period. This misalignment caused the seasons to drift, prompting the development of more accurate calendars.

Rome later adopted the Republican calendar, modeled after Greek conventions that assumed a 29.5‑day lunar month and about 12.5 synodic months per solar year, synchronized every fourth year by inserting intercalary months of January and February. Various reforms tried to bring this calendar into line with the solar year, including occasional extra months. In 46 BC Julius Caesar overhauled the system, adding ten days to the year to reach 365 days and instituting a leap day every fourth year, thereby decoupling the calendar from direct moon observations.

Even after Caesar’s changes, the Julian calendar continued to drift—about eleven minutes each year—relative to the equinoxes and solstices. By 1582 the discrepancy had grown to ten days. Pope Gregory XIII corrected this by skipping ten calendar days, so the day after 4 October 1582 became 15 October 1582, and he refined the leap‑year rule: century years are leap years only if divisible by 400. These adjustments reduced the calendar error from one day every 128 years to roughly one day every 3,030 years.

The adoption of the Gregorian calendar occurred slowly over a period of centuries, and despite many proposals to further reform the calendar, the Gregorian Calendar still prevails as the most commonly used dating system worldwide.

Holidays

A holiday designates a day—by tradition or law—when normal activities such as work or school are paused or reduced. The meaning of the word "holiday" varies by region: in the United States it most often refers to public or cultural observances, while the term "vacation" describes paid leave. In the United Kingdom and many former British colonies, "holiday" can also mean a period of paid time off.

Holidays generally commemorate events, individuals, or cultural and religious themes. While holidays like Christmas and New Year’s Day enjoy worldwide recognition, each nation maintains its own roster of observances, and even shared holidays may be celebrated differently within a country—some with complete shutdowns, others with partial closures. Certain nations, such as Brazil, experience near‑total suspension of business during events like Carnaval, which can extend for almost a week.

This tool primarily supports United States holidays, though users can manually add holidays from any country and optionally exclude specific dates. In the U.S., federal holidays are those officially recognized by the government, during which non‑essential federal offices close and employees receive paid leave. Private‑sector observance of these holidays varies by employer, and employees who work on a federal holiday may be entitled to additional holiday pay.

Some observances, like New Year’s Day, are "fixed" holidays—they occur on the same calendar date each year. Others, such as Martin Luther King Jr. Day, are "floating" holidays that fall on a specific weekday of a month (the third Monday in January, in this case). Thanksgiving is another floating holiday, taking place on the fourth Thursday of November, so its date changes annually. Below are tables listing the U.S. federal holidays for 2026 and 2027.

2026 U.S. Federal Holidays

2027 U.S. Federal Holidays