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Date Calculator

Calculate date differences, add/subtract days, working days

Date Difference Calculator

About the Date Calculator

Figuring out the exact number of days between two dates, or landing on the date a set number of days from now, is the kind of arithmetic that's easy to get wrong by hand — leap years, month lengths, and calendar quirks all trip people up. The Date Calculator handles this instantly: pick two dates and get the exact number of days, weeks, months, and years between them, or start from one date and add or subtract days to find where you land. It's built for the moments you actually need this — counting down to a deadline, checking how many days are left until a trip, working out a due date, or verifying how long ago something happened.

The calculator is split into six tabs. Date Difference gives the span between two dates as years, months and days, plus total days and a count of weekdays and weekend days. Add/Subtract moves a base date forward or back by a number of days, weeks, months or years and shows the weekday of the result. Age Calculator works out an exact age on any date you choose, Countdown shows the time left until a target date, Workdays counts Monday-to-Friday days in a range (optionally skipping New Year's Day, Independence Day and Christmas), and Day of Week tells you which weekday a date falls on.

Every tab recalculates as you type, so you can try a few scenarios back to back. Contract terms, billing cycles, warranty periods and project timelines all hinge on precise day counts, and that is where off-by-one errors creep in — so check whether the figure you need counts the end date or not. In this tool, Total Days is end minus start, while the Workdays tab and the weekday/weekend counts include both the first and the last day.

How to calculate days between dates

Use the Date Calculator to find the exact difference between two dates or to add/subtract days from a date.

  1. 1

    Choose a tab

    Pick Date Difference, Add/Subtract, Age Calculator, Countdown, Workdays or Day of Week, depending on the question you are answering.

  2. 2

    Enter your start date

    Pick the first date (start, base, birth or target date) using the date picker or type it in directly.

  3. 3

    Enter the second date or amount

    For a difference or workdays count, enter the end date. For Add/Subtract, click Add or Subtract, type a number and choose Days, Weeks, Months or Years.

  4. 4

    Review the result

    The result appears next to the inputs as soon as both values are filled in — a years/months/days breakdown with day counts, or the resulting date with its weekday.

  5. 5

    Adjust and recalculate as needed

    Change either date or the day count to test another scenario — the result updates immediately with no page reload.

Worked examples

Exact age on a given day

Input
Age Calculator tab — Birth Date 1990-06-15, Calculate Age On 2026-09-29
Result
36 Years Old · 3 Months · 14 Days · 13,255 Total Days Lived

Working days in December

Input
Workdays tab — Start Date 2026-12-01, End Date 2026-12-31
Result
23 Business Days; 22 with "Exclude US Federal Holidays" ticked

Both the start and end dates are counted. Christmas Day (Friday 25 December) is the only listed holiday that falls on a weekday in this range.

Span of a calendar year

Input
Date Difference tab — Start Date 2026-01-01, End Date 2026-12-31
Result
Total Time 0y 11m 30d · Total Days 364 · Weekdays 261 · Weekends 104

Total Days is the gap between the dates (end minus start), while Weekdays and Weekends count every calendar day in the range including both ends — which is why they add up to 365.

How long is a two-week sprint?

Input
Date Difference tab — Start Date 2026-03-02 (Monday), End Date 2026-03-13 (Friday)
Result
Total Time 0y 0m 11d · Total Days 11 · Weekdays 10 · Weekends 2

Eleven days elapse, but the sprint occupies 12 calendar days and 10 working days because both the first Monday and the last Friday are counted. The Workdays tab gives the same 10 for this range.

Tips and common mistakes

  • Add/Subtract has no "skip weekends" option. To land on the tenth working day after Friday 2 October 2026, add 14 days (two full weeks) to reach Friday 16 October — adding 10 days gives Monday 12 October, which is only the sixth working day. For longer runs, count the weekdays with the Workdays tab and adjust.
  • The six tabs keep their own inputs, so you can fill in the Age Calculator, switch to Countdown, and come back without losing anything. The Countdown and Day of Week tabs share one date field.
  • The holiday option in the Workdays tab only knows three fixed-date US holidays: New Year's Day (1 January), Independence Day (4 July) and Christmas Day (25 December). Holidays that move, such as Memorial Day, Labor Day and Thanksgiving, and "observed" days when a holiday lands on a weekend, are not removed — subtract those yourself.
  • Add/Subtract takes one amount and one unit. To add "1 year and 3 months", run it twice: add 1 year, then use the result as the new base date and add 3 months.
  • Month and year arithmetic rolls over rather than clamping to the month end: 31 January 2026 plus 1 month gives 3 March 2026, and 29 February 2024 plus 1 year gives 1 March 2025. Check results that start on the 29th, 30th or 31st.
  • Countdown counts whole calendar days from today to the target date, so it reads the same at any time of day and shows 0 on the target date itself. It does not show hours or minutes remaining.

Frequently Asked Questions

What date calculations can this tool perform?

It has six tabs: the difference between two dates (years/months/days, total days, weekdays and weekends), adding or subtracting days, weeks, months or years, an age calculator, a countdown to a target date, a workdays counter, and a day-of-the-week finder.

Can I calculate working days excluding weekends?

Yes. The Workdays tab counts Monday to Friday between two dates, including both ends. Ticking "Exclude US Federal Holidays" also removes New Year's Day, Independence Day and Christmas Day when they fall on a weekday; other public holidays are not included.

How does the calculator handle the end of a month?

It rolls over rather than clamping. If the day does not exist in the target month, the extra days carry into the next month: 31 March plus 1 month gives 1 May, and 31 January 2026 plus 1 month gives 3 March 2026. If you need "the last day of next month", check the result or add days instead.

Does the calculator account for leap years?

Yes. Day counts use the real calendar, so Total Days from 1 February to 1 March is 29 in 2024 and 28 in 2026, and the Age Calculator counts 29 February birthdays correctly. Only the Quick References are approximations: a year is listed as 365.25 days and a month as 30.44.

Does Total Days include both the start and end date?

No — Total Days is end minus start, so Monday 2 March to Friday 13 March 2026 is 11 days. If you count a booking or leave request "inclusively", add 1. The Weekdays and Weekends figures on the same tab, and the Workdays tab, do include both ends: the same range shows 10 weekdays and 2 weekend days, and 10 workdays.

What happened to the Date Calculator in the Time Tools section?

It was merged into this page in October 2026 and its old address now redirects here. If you used it: that version counted the end date by default, so its Total Days was one higher than the end-minus-start figure shown here (add 1 for the inclusive count), and its "exclude weekends" switch is replaced by the Workdays tab, which counts Monday to Friday including both ends. To combine years, months and days in one step, add them one unit at a time, largest first.

Can I print or save the result?

Use Print Results at the bottom of the tool to open your browser's print dialog, where you can also choose "Save as PDF". The Add/Subtract tab also has a Copy Result button for the resulting date.