How does the "Include end date" option work?

By default, our calculator counts the difference between the two dates excluding one of them. When you enable "Include end date", it counts both the start and end days, adding 1 to the total. This is useful for counting inclusive date ranges, like the number of days of a hotel stay.

Does the calculator handle leap years correctly?

Yes. The calculation uses the standard Gregorian calendar rules, so leap years (with 366 days, where February has 29 days) are fully accounted for. If you add 1 year to February 29, 2024, you will correctly get February 28, 2025.

What is the ISO week number?

The ISO week number is a standard way of numbering weeks within a year, used by businesses and governments worldwide. Week 1 is the week containing the first Thursday of the year. Our calculator shows the ISO week number of the resulting date.

How do I use presets like "Last week" or "Last month"?

In the Difference mode, click any preset button to quickly fill the "From Date" with the appropriate date. For example, "Last week" sets the From date to exactly 7 days before today, making it easy to calculate weekly reports or review past periods.

Is my date input saved or shared?

No. All calculations happen entirely in your browser using JavaScript. Your dates are never sent to any server, stored, or shared. Even if you disconnect from the internet, the tool continues to work.

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date calculator

Q: What is a date calculator?

A date calculator is a tool that helps you work with dates in two main ways: finding the difference between two dates (for example, how many days between two events), and adding or subtracting days, weeks, months, or years from a starting date to get a new date.

Q: Can I add months to a date like January 31?

Yes. When you add 1 month to January 31, the result depends on the target month. If the target month has fewer days (like February), the result rolls to the last day of that month. Our calculator uses standard JavaScript Date logic, which handles this automatically.

Q: Can I calculate the number of working days between two dates?

This calculator shows total calendar days, not working days. For a business-day calculation (excluding weekends and holidays), you would need a dedicated business day calculator. However, the total days shown here can be a useful starting point for manual calculation.

Calculate the difference between two dates, or add and subtract days, weeks, months, and years.

From Date

To Date

Include end date (count both start and end days)

Start Date

Operation

Amount

Years

Months

Weeks

Days

About Our Date Calculator

Using dates can be very confusing! Be it deadlines, anniversaries, holiday dates, project dates, contracts or medical dates. How many days between now and December 31st? What date will it be if I add 6 months to January 31st? How many weeks until I have my holiday?

Our date calculator can help you with all of these questions instantly. It has two functions, one to find the exact time between dates and the second to add or subtract days, weeks, months and years. It takes into account leap years, different number of days in months and handles all of the edge cases.

Using Our Date Calculator

There are two functions available:

Date Difference

Click the 'Difference Between Dates' tab.
Type your 'From Date' and 'To Date'.
Click the quick date buttons (Today, Last week, Last month) to automatically populate your 'From' date.
Check the box for 'Include end date' if you want to include both the start and end date (Useful for calculating dates for hotel stays, subscriptions etc).
Instantly the calculator will give you the result showing you the exact number of years, months and days and the total number of days, weeks, hours and minutes.

Add / Subtract

Click the 'Add / Subtract' tab.
Type your 'Start Date'.
Select whether you want to 'Add' or 'Subtract'.
Now type in the number of years, months, weeks and / or days you want to add or subtract. You can add any combination of years, months, weeks and days.
The calculator will show you the new date including the day of the week, ISO week number and how many days left in the year.

Why Use Our Date Calculator

Whilst there are many date calculators online, we have made ours with a couple of key features.

We have two calculators in one!
Our calculator accounts for leap years and different numbers of days in each month.
We give you a detailed result showing you the exact number of years, months and days rather than just the total number of days.
When adding or subtracting, we give you more information such as the day of the week, ISO week number and days left in the year.
Your data is secure as everything is calculated in your browser.

Popular Uses For A Date Calculator

People use date calculators for:

Finding someone's exact age or length of time worked.
Find out how many days until their holiday, wedding or deadline.
Calculate how many days are left on their project.
Calculate legal deadlines (30/60 days etc).
Find out when their subscriptions / contracts finish.
Plan events and check availability.
Calculate approximate business days.

How Is It Calculated?

The date difference is a little more complex. We look at the year, month and day separately to give you an accurate result. If the day of your end date is less than the day of your start date we minus one month from the month and add the number of days in that month.

When adding or subtracting we simply add the years, months, weeks and days in that order. Using standard JavaScript Date functions.

FAQs

What is a date calculator?

A date calculator can help you find the difference between dates or add / subtract days, weeks, months and years to a start date.

What does Include end date mean?

By default we will calculate the difference between your dates without including either date. If you select Include end date we will include both the start and end date. This adds an extra day onto your result. This is useful in determining the period of time between two dates, like when you stayed in the hotel.

Does it consider leap years?

Yes! We use standard Gregorian calendar rules. Leap years (366 days, February has 29 days) are taken into account. Adding 1 year to February 29th 2024 will give you February 28th 2025.

Can I add months to a date like January 31st?

Yes! If you add 1 month to January 31st it will depend on what month you are adding. If the month has fewer days (February) it will show you the last day of that month. We use standard JavaScript Date functions.

What is an ISO week number?

An ISO week number is a standardised way of showing the week number. Used globally in businesses and government. The first week of the year is the week that contains the first Thursday. Our calculator will show you the ISO week number.

How do I use the quick date buttons?

When using the Date Difference function you can click any of the buttons to quickly add the correct date to your 'From Date'. For example, clicking Last week will add exactly 7 days to your 'From' date.

Will my date be saved / shared?

No! All calculations are completed in your browser using JavaScript. We will never send your dates to a server or save them. You can even use our calculator whilst offline.

Can I calculate the number of working days between two dates?

No. This calculator will only show you the total number of days. If you want to know how many working days (Not including weekends and holidays) you will need to use our Business Day Calculator. However, the total number of days can be a good starting point when calculating manually.

Other Tools You May Like

If you found our date calculator useful you may also like our Age Calculator to track someone's exact age, Percentage Calculator to do some quick maths or BMI Calculator.