Date Duration Calculator

Q: Can I include the end date in the count?

Yes. Check the box that says Include end day (add 1 day) . This adds one extra day to the total. It is useful when you want to count both the start date and the end date as full days.

Q: How do I exclude weekends from the count?

Check the box that says Exclude weekends (Sat & Sun) . The calculator will skip all Saturdays and Sundays and only count weekdays. The Excluded Days Info section will show you how many weekend days were removed.

Q: How do I exclude holidays from the duration?

Click Holiday Settings to open the holiday panel. Check the box for Exclude holidays from duration count . Then pick which holidays you want excluded. U.S. federal holidays are checked by default, and you can also add your own custom holidays.

Q: Can I add my own custom holidays?

Yes. In the Holiday Settings panel, scroll to the Custom Holidays section. Type a name, pick a month, and enter the day. You can add up to 20 custom holidays by clicking the Add more button.

Date Duration Calculator

Updated Sep 1, 2026 By Jehan Wadia

Introduction

The Date Duration Calculator helps you find the exact number of days, months, and years between two dates. Whether you need to know how many days until a big event, how long you've been alive, or the time between any two dates, this tool gives you a quick and clear answer. Just pick a start date and an end date, and the calculator returns the length of time between them. It's a simple way to measure the passage of time without counting on a calendar by hand.

How to Use Our Date Duration Calculator

Enter a start date and an end date to find out how many days, weeks, months, or years are between them.

Start Date: Pick the first date. This is the earlier date you want to count from. You can type it in or use the calendar picker.

End Date: Pick the second date. This is the later date you want to count to. You can type it in or use the calendar picker.

A date duration calculator finds the amount of time between two dates. It counts the total number of days, weeks, months, and years from one date to another. This is useful when you need to know how many days are left until an event, how long ago something happened, or the exact length of time between any two dates.

How Date Duration Works

Every date sits on a timeline. When you pick a start date and an end date, the calculator counts every single day in between. It can also break that count into larger units like weeks, months, and years. For example, if you pick January 1 and March 1 of the same year, the result would be 59 days (or 60 days in a leap year).

Why Counting Days Can Be Tricky

Not all months have the same number of days. Some months have 30 days, others have 31, and February has 28 or 29. This means counting months between two dates is not always simple. A year is usually 365 days, but a leap year adds one extra day in February, making it 366 days. Leap years happen every 4 years, with a few exceptions. These differences matter when you need an exact count.

Common Uses for a Date Duration Calculator

Project deadlines: Find out how many days you have to finish a task. Tools like a Lead Time Calculator can also help you plan timelines for deliveries and production schedules.
Age calculation: Figure out your exact age in days, months, or years. Our dedicated Age Calculator is specifically designed for this purpose.
Event planning: Count the days until a birthday, wedding, or holiday.
Legal and business needs: Many contracts and laws depend on exact day counts, such as a 90-day notice period or a 30-day return policy.
Travel planning: Know the exact length of your trip in days.

Inclusive vs. Exclusive Counting

When counting days between two dates, you can count in two ways. Exclusive counting does not include the start date or the end date. Inclusive counting includes both the start and end dates. For example, from Monday to Wednesday is 2 days exclusive but 3 days inclusive. Which method you use depends on your situation. Many date calculators use exclusive counting by default, meaning they count the days between the two dates.

Formulas used

Total Difference (milliseconds)

\Delta_{ms} = t_{end} - t_{start} + \begin{cases} 86400000 & \text{if include end day} \\ 0 & \text{otherwise} \end{cases}

Total Seconds / Minutes / Hours

S = \left\lfloor \frac{\Delta_{ms}}{1000} \right\rfloor, \quad M = \frac{S}{60}, \quad H = \frac{M}{60}

Total Days and Weeks

D = \frac{H}{24}, \quad W = \frac{D}{7}

Total Months (approximate)

M_{total} = \frac{D}{30.4375}

Total Years (approximate)

Y_{total} = \frac{D}{365.25}

Business / Counted Days

D_{business} = \lfloor D \rfloor - D_{weekends} - D_{holidays}

Frequently asked questions

Can I include the end date in the count?

Yes. Check the box that says Include end day (add 1 day). This adds one extra day to the total. It is useful when you want to count both the start date and the end date as full days.

What happens if my start date is after my end date?

The calculator will automatically swap the dates and still give you a correct result. You will see a small yellow badge that says Dates were swapped so you know it made the switch.

How do I exclude weekends from the count?

Check the box that says Exclude weekends (Sat & Sun). The calculator will skip all Saturdays and Sundays and only count weekdays. The Excluded Days Info section will show you how many weekend days were removed.

How do I exclude holidays from the duration?

Click Holiday Settings to open the holiday panel. Check the box for Exclude holidays from duration count. Then pick which holidays you want excluded. U.S. federal holidays are checked by default, and you can also add your own custom holidays.

Can I add my own custom holidays?

Yes. In the Holiday Settings panel, scroll to the Custom Holidays section. Type a name, pick a month, and enter the day. You can add up to 20 custom holidays by clicking the Add more button.

What are business days and how are they counted?

Business days are weekdays that are not holidays. When you exclude weekends and holidays, the Business / Counted Days number shows how many working days fall between your two dates. This is helpful for work deadlines and shipping estimates.

Date Duration Calculator

Full Duration Breakdown

Total In Each Unit

Excluded Days Info

Visual Breakdown

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Introduction

How to Use Our Date Duration Calculator