How many days between dates

If you are trying to meet your project deadline, counting down to your vacation, or just curious; the question “how many days are there between two dates?” is more common than you think. Counting manually on a calendar is inconvenient and error-prone. Fortunately, there are much easier ways!

Our tool not only allows you to calculate the number of days between two dates. This is ideal for planning important dates such as birthdays, events or determining the time to a certain date.

In this macro, we show you how to calculate the number of days between a start and end date at lightning speed. We not only provide you with a super handy online tool, but also give the techies among us a JavaScript macro to automate the calculation themselves.

Calculating the period between two dates is a common task in both personal and professional contexts. It is essential to know exactly how much time is between two dates. Correctly calculating the period between two dates not only helps you organize and plan important events, but also prevents misunderstandings and errors in your planning. In this article you will discover different ways to calculate the period between two dates, from using a handy calculation tool to performing a calculation yourself. In addition, we explain why it is important to take leap years and other factors into account that can affect the outcome. This way you can always be sure of a reliable and accurate calculation, regardless of the situation.

Calculate it with our data calculator

Need an immediate answer? No problem! Enter the start date and end date below, select the desired dates and our calculator will do the rest. The results of your calculations are displayed instantly. It couldn’t be simpler.

You can use this tool to calculate not only the number of days between two dates, but also the number of weeks, months, years, working days, weekends and holidays. If you want to calculate the number of working days or the number of days of weeks between two dates, you can easily choose that.

You can choose to include or exclude the end date, and you can add or subtract periods such as weeks, months or years from a date. This allows you to quickly calculate a period or determine the end of a project.

Tip: Make sure you have entered the correct start date and end date before performing the calculation so that the results are correct.

For developers: calculate the number of days with a JavaScript macro

Are you a developer or find it interesting to see how the magic works behind the scenes? With a small piece of JavaScript, you can easily apply this calculation in your own projects.

This is a simple and effective function (or “macro”) for calculating the difference in days between two date strings. You can also extend this approach to calculate the difference in weeks, months, years, hours or even times between two date strings. This way you can easily calculate different periods depending on what you want to know. For example, it is useful if you want to determine the period between a start and end date, or if you want to know how many days, weeks, months or years are between two dates. You can also use JavaScript to easily subtract months or years from a given date.

Example: subtracting a month from a date:

const datum = new Date('2024-07-15');
datum.setMonth(datum.getMonth() - 1); // Remove one month
console.log(datum.toISOString().slice(0,10)); // Output: 2024-06-15

Example: subtracting a year from a date:

const datum = new Date('2024-07-15');
datum.setFullYear(datum.getFullYear() - 1); // Remove one year
console.log(datum.toISOString().slice(0,10)); // Output: 2023-07-15

So with these methods, you can calculate or subtract not only days, but also weeks, months, years, hours or times. This makes your calculations flexible for all kinds of applications, such as calculating the period between two dates, planning projects or tracking events.

/**
 * Calculates the number of full days between two dates.
 * @param {string} date1 - The start date in 'YYYY-MM-DD' format.
 * @param {string} date2 - The end date in 'YYYY-MM-DD' format.
 * @returns {number} The number of days between the two dates.
 */
function calculateDaysBetweenDates(date1, date2) {
  // 1. Create Date objects from the input strings.
  const dateObject1 = new Date(date1);
  const dateObject2 = new Date(date2);

  // 2. Calculate the difference in milliseconds.
  const differenceInTime = dateObject2.getTime() - dateObject1.getTime();

  // 3. Convert the difference to days.
  // (1000 milliseconds * 60 seconds * 60 minutes * 24 hours)
  const differenceInDays = Math.round(differenceInTime / (1000 * 3600 * 24));

  return differenceInDays;
}

// Example of how to use the function:
const startDate = '2024-07-01';
const endDate = '2024-07-31';
const numberOfDays = calculateDaysBetweenDates(startDate, endDate);

console.log(`There are ${numberOfDays} days between ${startDate} and ${endDate}.`);
// Output: There are 30 days between 2024-07-01 and 2024-07-31.

How does this code work?

1. Create Date objects: the function accepts two dates as text (for example, ‘2024-07-01’). JavaScript converts these to Date objects, which it can use to calculate.
2. Difference in milliseconds: the .getTime() method returns the number of milliseconds that have elapsed since January 1, 1970. By subtracting these values, we get the exact time difference.
3. Convert to days: we know how many milliseconds are in one day (1000 60 60 * 24 = 86,400,000). We divide the total difference by this number to get the number of days. Math.round() is used to neatly round the number.

You can easily adjust this calculation to determine the difference in weeks, months, years, hours or times. Depending on the unit of time chosen (days, weeks, months, years, hours or times), the results of the calculations will differ. For example, you can calculate the number of weeks between two dates by dividing the number of days by 7, or determine the number of months and years with specific date functions. This is useful for planning projects, measuring periods and getting accurate results in different calculations.

Note: ‘Between’ versus ‘Up to and including’

An important nuance in counting days is whether you include the end date itself. You can choose whether or not to include the end date in the calculation. Our tool and script calculate the number of full days between the start and end date. Sometimes you have to subtract or add a day, depending on your choice. Please note that this choice will affect the results.

Example: There are 2 days between July 1 and July 3 (July 2 and July 3 themselves are not considered a full 24-hour period after the start). If you want to know the period from July 1 to July 3 (i.e., July 1, 2 and 3), count 3 days. In that case, add 1 day to the result.

Avoiding errors when calculating days

When calculating the number of days between two dates, it is important to avoid common mistakes. One of the biggest pitfalls is forgetting leap years. This is because a leap year counts 366 days instead of 365, making the period between two dates sometimes a day longer than you would expect. Entering the start date or end date incorrectly can also lead to an incorrect calculation of the period between two dates. To avoid this, it is wise to always use a reliable and convenient calculation tool, or a program such as Excel in which you can enter dates accurately. Always check carefully that you have entered the correct dates and that you have taken into account all relevant factors, such as leap years and the correct order of dates. By working carefully and using reliable tools, you will avoid mistakes and be sure that your calculation of the period between two dates is always correct.