Days Calculator

1. How to do days calculations
2. How many days are there between two dates?
3. How many days until a date
4. How many days since a date
5. Time between dates
6. Adding days to a date
7. What calendar do we use?

    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 the days between dates 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 are between June 23rd and September 15th 2026. If you choose to exclude the final day, the result will be 84 days. If you wish to include the last day in the result, this would be 84+1, resulting in 85 days total.

This days calculator can be used to find the number of days between any two calendar dates e.g. days since a date in the past till today, or days from a given date till now. Wondering how many days are between Thanksgiving and Independence day? How many days between Halloween and Thanksgiving? Our tool has the answers for any date to date question - simply enter the two dates of interest.

    How many days are there between two dates?

It may look like a simple question, but the answer actually depends on the definition of what is meant by a "day" in the context of the question. There are three most common approaches required in most problems of calculating the time between dates.

Calendar days

With calendar days one needs to simply calculate how many days there are between the given dates. The math is straightforward with the only complications arising when the time span includes the end of one or more years. That complication is factoring in leap years. Leap years are years with an extra day (versus a regular year) and 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 every 100 years ^[3].

Say you are an expecting parent and today is the first day of November. If the due date is before the end of February next year then leap years do not matter, but if it is after that they may. If the following year is a leap one, then there would be one extra day between today and the due date as opposed to if it was a typical year. This days between calculator takes into account leap years automatically and so does our counter for the count of days between two dates.

Weekdays

In some scenarios one is only interested in how many weekdays there are between two dates. This happens in business when one may state a contract term or offer to perform a given service in N weekdays. However, it is more common to state such terms in business days, as discussed below.

Working days

It is common for business contracts to state the execution time for a certain amount of work, or the delivery terms for goods or services in terms of business days, otherwise known as working days or "bank days" in some cases. While it varies by country, in general working days include all weekdays minus any official holidays such as those due to important state or religious holidays.

    How many days until a date

Regardless if talking about calendar days, weekdays, or just working days, counting how many days are until a particular date is the same as calculating the number of days between two dates. That is, assuming we know the date of the event of interest. The main complication remains the same and it is that different months have varying number of days. If you're looking to do the math manually, you'll need to advance to the next month every 28, 29, 30 or 31 days, depending on the particular month, with the remainder in the end being the particular date of the final month you arrive at.

Using our date calculator makes things much easier. Say we have an arrangement for the end of July. To check how many days until July 31, simply enter today's date (May 18, 2026) in the first field and July 31 in the second.

Days until date

The table below features a quick reference for the number of days until upcoming dates.

For example, to see how long until June 1, 2026 just look up its row to see the number of days and weeks from today until that date.

    How many days since a date

Calculating how long it has been since a date in the past requires calendar calculations just like the ones for checking how many days are from today to a date in the future. If the date is very recent, the number of days since can be calculated as a simple subtraction. For example, to calculate how many days are from May 5 to May 15 all that is needed is to subtract 5 from 15 to get the result, which is 10.

If the from date and to date fall into different months, you need to take into account how many days each month in between the dates has. It can be 30, 31, 28 or 29 (February in leap years). In such cases a days calculator becomes extremely convenient.

Days since date

The table is a quick reference for the number of days that has elapsed since dates from the recent past.

For example, to see how many days have passed since May 4, 2026 check its row to see how many days and weeks are from that date to today.

    Time between dates

While calculating how many days are there between dates, it is a bit more complicated when other time measurement units are concerned. Here is how to convert the time between dates into weeks, months, years, and even centuries.

Weeks between dates

Starting from the number of days between the dates, it is very easy to find the number of weeks between them since a week has a strict definition that does not change depending on the calendar time. Simply divide the number of days by seven. For example, if our days calculator says there are 28 days between two dates, the number of weeks is calculated as 28 / 7 = 4 full weeks.

Months between dates

To find out the number of months between two dates, one needs to consider the order in which months duration changes, as well as leap years. Some months have 31 days, others have 30 days, and February has either 28 or 29 days depending on it being a leap year or not. For more details see our months between dates calculator.

Years between dates

The number of years between any two dates is a bit easier to calculate. A year has either 365 days for a regular year or 366 days for a leap year. You can use a leap year calculator to count the number of leap years between the days. To calculate the number of years from the days between the dates:

1. Multiply the number of leap years by 365
2. Subtract the result from the number of days
3. Divide the remaining number by 365 and add it up with the number of leap years

The most straightforward interface for such tasks is in our how many years calculator.

    Adding days to a date

This calendar days calculator can be used to add any number of calendar days to a starting date. If you input a negative number of days to add, it will instead subtract that many days from the specified date. For adding business days, see our business days calculator which skips weekends and also official holidays in a specified country.

    What calendar do we use?

There are three main kinds of calendars currently being used around the world: solar, lunar and solilunar or lunisolar. The days between 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 1923, while it was adopted by the British Empire and most of its colonies, including its American colonies, 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 a 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.).

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 ^[2].

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.

Not remembering the length of all months or not knowing whether a particular year is a leap year or not may hinder you when trying to calculate days between dates. This tool covers all of these issues and all you need to know is the first and last date of the time interval you are interested in to accurately count days.