Days Between Two Dates Calculator: Easily calculate the number of years, months, weeks, and days between two dates. Simply enter your dates and get the precise duration. Click on “Settings” to customize your holiday settings for more accurate results.
History of the Gregorian Calendar
The Gregorian calendar is the most widely used calendar system in the world today. A standard year in this system consists of 365 days, with an additional leap day added to February during a leap year. The months of April, June, September, and November each have 30 days, while the other months have 31 days, except for February, which has 28 days in a common year and 29 days in a leap year.
This calendar is a reform of the Julian calendar, which itself was a modification of the ancient Roman calendar. The early Roman calendar was based on the lunar cycles and was believed to be an observational lunar calendar. Initially, the Romans used a 10-month calendar totaling 304 days, leaving about 50 days of unaccounted time during the winter months. This misalignment between the seasons prompted the need for a more accurate system.
The Roman Republican calendar followed the Greek method of calculating lunar cycles and solar years, with adjustments made every few years to better synchronize the months with the solar year. By 46 BC, Julius Caesar introduced a significant reform to the calendar, creating the Julian calendar. This involved adding 10 extra days to the year, bringing the total number of days to 365, and incorporating a leap day every four years to keep the calendar in sync with the seasons.
However, even after these reforms, the Julian calendar still experienced drift due to a small error that caused it to fall out of alignment with the equinoxes and solstices by about 11 minutes annually. By 1582, this drift had accumulated to 10 extra days. Pope Gregory XIII addressed this issue by eliminating 10 days from the calendar, declaring that October 4, 1582, would be followed by October 15. Additionally, the Gregorian calendar introduced a new rule regarding century years: century years not divisible by 400 would not be leap years. These changes significantly reduced the calendar error, reducing it from 1 day in 128 years to 1 day in 3,030 years.
The adoption of the Gregorian calendar was gradual and occurred over centuries. Despite several proposals for further calendar reforms, the Gregorian system remains the most commonly used dating system worldwide.
Holidays
A holiday is a day set aside for rest or commemoration, during which regular activities like work or school are suspended, at least partially. The meaning of "holiday" can vary depending on the region. In the United States, paid time off is commonly referred to as "vacation," while national, religious, or cultural observances are called "holidays." However, in some regions like the United Kingdom and former British colonies, "holiday" can also mean paid leave from work.
Holidays are typically established to commemorate significant events, people, or cultural or religious traditions. While some holidays, such as Christmas and New Year's Day, are celebrated globally, most countries have their own set of holidays, and the way they are observed can differ. For instance, in Brazil, Carnaval is a major holiday, often resulting in a week-long break, with only essential businesses operating.
This calculator is primarily designed for U.S. holidays, but it allows users to input holidays specific to other countries manually. Certain holidays can also be excluded from calculations. In the U.S., federal holidays refer to those recognized by the government, during which non-essential federal offices close and employees receive paid leave. In the private sector, however, observance of federal holidays varies by company, and employees required to work on such days may receive holiday pay in addition to their regular wages.
Some holidays, such as New Year's Day, are considered "fixed holidays" because they occur on the same date every year. Others, like Martin Luther King Jr. Day, are "floating holidays," meaning they occur on a specific weekday of the month, such as the third Monday in January. Similarly, Thanksgiving is a "floating Thursday," occurring on the fourth Thursday of November. Below are the dates of U.S. federal holidays for 2025 and 2026.