# How to Use: Date to Date Calculator

The Date to Date Calculator lets you find the number of days, months, and years between two dates.

## Getting Started with Your Calculation

1. First enter the Start Date and End Date by either
• using the input fields;
• clicking on the calendar icon to select your date;
• or clicking on the Today link to get today's date.
2. Then click Calculate Duration to get your result.

### Include end date

Checking Include end date in calculation counts the final day in your result.

If you want to count how many days something lasted, for example, an event that lasted from the 1st to and including the 4th day of the month, this should be checked (result: 4 days.) Otherwise, the last day would not be counted (returning 3 days).

If you want to calculate the age of something, leave this unchecked (the last/end date is not counted as one additional day).

The Add time fields link takes you to the Time Duration Calculator where you can add hours, minutes, and seconds to your calculation.

The Add time zone conversion link takes you to the Time Zone Duration Calculator where you can calculate the duration between a point in time in one time zone and a different point in time in another time zone.

### Remove holidays and weekends

The Count only workdays link takes you to the Business Date Calculator where you can exclude different days, like weekends and public holidays.

### Why are the years and months wrong?

The calculator adds or subtracts the larger time units before the smaller time units. This means that it adds years, then months, then days. Although the total number of days in January (31) and February (28) are different, both are counted as 1 month. In some cases, this method can lead to unexpected results.

For example, in a common year, the time span between January 28 and March 1 is calculated as 1 month and 1 day (January 28 + 1 month = February 28; February 28 + 1 day = March 1).

However, the time span between January 31 and March 1 is also shown as 1 month and 1 day. The calculator first adds 1 month to jump from January to February. But since February only has 28 days in a common year, it lands on February 28 before adding 1 day to arrive at March 1.

This may seem illogical at first, but the structure of our calendar means that there is no perfect way of calculating dates including months and years.

### Does the calculator include leap years?

Yes, all our calculators account for leap years.

### Does the calculator include leap seconds?

No, this calculator does not account for leap seconds.

### Does the calculator account for Daylight Saving Time (DST) clock changes?

No, this calculator does not take DST changes into account.

### Why are the date fields in the wrong order?

You can change the order of the Day, Month, and Year fields by selecting a different Short Date format in My Units.

### Can I edit my calculation?

To edit your calculation, scroll up to the top of the page, make your changes, and calculate again. The Make adjustment and calculate again is a shortcut to the top of the page.

### Can I exclude the first day in my results?

In our calculations the first day of the entered period is always included. However, we do have the option to include the end day. Try selecting the day after if you don't want a day to count.

### Why can I include the end date?

Checking Include end date in calculation counts the final day in your result.

If you want to count how many days something lasted, for example, an event that lasted from the 1st to and including the 4th day of the month, this should be checked (result: 4 days.) Otherwise, the last day would not be counted (returning 3 days).

If you want to calculate the age of something, leave this unchecked. See "What can I use the Date Duration Calculator for?" for 2 examples of calculations.

### How does your algorithm work? Can you help me program my own?

We are a small team with very extensive websites to manage, so, unfortunately, we do not have the capacity to share detailed information about our algorithms or provide programming help.

### Why does the result show the wrong days of the week?

This is most likely not an error but due to the fact that the Julian calendar was still in use in the year you entered. This calendar system was eventually replaced by today's Gregorian calendar, but the date this change happened differed from one country to another.

The calculator uses the Julian-Gregorian switch date of the country you select in the settings under My Units.

### What can I use the Date to Date Calculator for?

Here are 2 examples, with all the fields filled in, just click the Calculate duration after following the links.

### What kinds of date calculators do you offer?

1. Calculating the duration between 2 points in time: