Days Between Dates Calculator

Use this calculator to easily calculate the days between any given two dates.

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How to do days calculations

Sometimes you just need to find out how many days you have to finish an assignment or how long a trip is going to be. Using this calculator is easy and quick as long as you have the first and the last date of the period of time you are interested in. You can choose whether to include the last day in the calculations or not.

Example: You need to find out how many days between June 23rd and September 15th 2018. If you choose to exclude the final day, the calculator will show you 84 days. If you wish to include the last day in the result, this would be 84+1, resulting in 85 days total.

What calendar do we use?

There are three main kinds of calendars currently being used around the world: solar, lunar and solilunar or lunisolar. This calculator is based on the Gregorian calendar, which contains 365 days in a typical year and 366 in a leap year. This is a solar calendar named after Pope Gregory XIII who introduced it in 1582. It was first used in Catholic countries in Europe, consequently replacing the Julian calendar (introduced earlier by Julius Caesar) which it is based on, the Islamic, and others. Greece was the last European country to adopt it in in 1923, while it was adopted in the British Empire and most of its colonies, including American, in 1752.

The calendar is currently used throughout most of the world. Some countries have chosen to modify it, others use it alongside their old calendars. There are only few who have not adopted it at all to this point.

Most countries use the Gregorian as their civil calendar, which means it is used for general everyday purposes: administrative, civil, and official. Typically these countries would also have other calendars used simultaneously, such as ones based on religion (Christian Orthodox, Catholic, Islamic, Hebrew, etc.).

This days calculator does take into account leap years. Leap years are necessary in order to keep the calendar in alignment with Earth’s revolutions around the Sun, as it takes about 365 days, 5 hours and 48 minutes for Earth to make a full circle. If leap years are not calculated into the calendar, we would lose about 24 days in 100 years [2].

There are about forty calendars in the world, including the Chinese, the Persian, the Mayan, the Egyptian, the Islamic, the Bulgar, the Hijri, the Roman [1].

calendar days

Due to the change in calendars in the West, there exist the terms Old Style (OS) and New Style (NS). They are found in history books where historians are referring to past events which took place when the Julian calendar was used. These styles were also use by people at the times when the change was happening to make it clearer, especially when writing letters and other documents.

Today there are many proposals to reform the calendar in order to make it easier to use. Criticisms of the calendar include that it is not perennial, meaning it starts on a different week day each year, which also means that it expires on the 31st of December. In addition the months differ in length in a non-logical way for the common person. Some criticize it for being based on religious events and that it is not connected to the lunar phases. However, we still use the version adopted centuries ago with no prospects of this changing anytime soon.

Not to worry, however, if you have trouble counting or calculating days between dates due to not remembering the length of the months or whether it is a leap year or not. This calculator covers all of these issues and all you need to know is the first and last days of the period of time you are interested in.


[1] Calendars. (n.d.). In Wikipedia. Available at

[2] "What Is a Leap Year?". Available at

Cite this calculator & page

If you'd like to cite this online calculator resource and information as provided on the page, you can use the following citation:
Georgiev G.Z., "Days Calculator", [online] Available at: URL [Accessed Date: 26 May, 2018].