Date Calculator

What is a date calculator?

A date calculator answers the date questions that come up in everyday life. How many days are left until a deadline? How long ago did something happen? What will the date be 90 days from today? Instead of counting squares on a calendar, you pick the dates, and the answer appears instantly in days, weeks, months and years.

Our date calculator has two tools in one. The first finds the days between two dates. The second adds or subtracts days, weeks, months and years from a date you choose. Both work for any date from the year 1000 to the year 9999.

How to calculate the days between two dates

You can do it by hand in a few steps. Count the days left in the start month, add the days of each full month in between, then add the days of the last month. Take 1 March 2026 and 15 June 2026. There are 31 days from 1 March to 1 April, 30 days to 1 May, 31 days to 1 June and 14 more days to 15 June. Add them up: 31 + 30 + 31 + 14 = 106 days, which is 3 months and 14 days.

The calculator does the same thing without mistakes. It also handles months of different lengths and leap years, which are the two places where hand counting usually goes wrong.

Include the end date or not?

By default, the difference between two dates does not count the last day. From 1 January to 7 January the difference is 6 days. If you need to count both the first and the last day, for example the days of a holiday or a course, tick the option to include the end date. The same range then becomes 7 days.

A simple rule helps: count the nights between the dates for a hotel stay, and count both ends for the number of days you are away.

Add or subtract days, weeks, months and years

The second tool starts from a date and moves forward or backward. Choose add or subtract, then fill in any mix of years, months, weeks and days. These examples show how it works:

• 30 days after 1 January 2026: 31 January 2026.
• 90 days after 1 January 2026: 1 April 2026, a Wednesday.
• 6 weeks before 15 June 2026: 4 May 2026.
• 1 month after 31 January: 28 February in a normal year, or 29 February in a leap year, because February has no 31st.

Weekdays and weekend days

Along with the total, the calculator shows how many of the days are weekdays, Monday to Friday, and how many fall on a Saturday or Sunday. This is a quick way to estimate working days for a project, a delivery or a notice period.

Public holidays are different in every country and company, so they are not removed automatically. Count the holidays in your range yourself and subtract them from the number of weekdays.

When do you need a date calculator?

• Deadlines and projects: Find how many days or working days are left until a due date.
• Payment terms: Work out the due date of an invoice that must be paid in 30, 45 or 60 days.
• Notice periods: Check the last day of a notice period in a job, rental or contract.
• Returns and warranties: See whether a 14, 30 or 90 day window is still open.
• Travel planning: Count the days of a trip or the days until you travel.
• Study and exams: Plan your revision by counting the days left before an exam.
• Events and milestones: Count down to a wedding, a birthday or an anniversary.

How leap years change the result

A normal year has 365 days and a leap year has 366, because 29 February is added. From 1 January 2028 to 1 January 2029 there are 366 days, since 2028 is a leap year, while from 1 January 2026 to 1 January 2027 there are 365 days. The calculator uses real calendar dates, so every leap day is counted for you.

Common date calculation mistakes

• Treating every month as 30 days: Months have 28 to 31 days, so multiplying months by 30 gives a wrong total.
• Forgetting leap days: A range that crosses 29 February has one extra day.
• Counting the end date by accident: Decide first whether the last day should be included.
• Mixing up date formats: The date 04/10/2026 means 4 October in many countries and 10 April in others, so always check the order.
• Ignoring weekends and holidays: A deadline in working days is shorter than the same number of calendar days.

Why use our free date calculator?

• Two tools in one: Days between dates, and add or subtract time, on the same page.
• More than days: You also get weeks, hours, months, years, weekdays and weekend days.
• Accurate: Leap years and different month lengths are handled for you.
• Private: Your dates stay in your browser and are never uploaded.
• Free: No signup, no limits and nothing to install.