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Date Difference Calculator

Count days, weeks and working days between two dates.

Enter either date first: the order is adjusted automatically

A sample is prefilled; feel free to change it

How to use

  1. Pick a "Start date" and an "End date": results update live as you choose. If the dates are entered in reverse order they are swapped automatically and you get a hint.
  2. "Total days apart" counts whole days between the two dates and does not include the start day: January 1 to January 2 is 1 day. Working days follow the same rule.
  3. Tick "Exclude weekends" to also see how many working days (Monday to Friday) fall in the interval.
  4. Weeks are shown as full weeks plus remaining days; months and years are estimates based on 30.44 days per month and 365.25 days per year.
  5. Click "Copy result" to copy every figure at once, ready to paste into a document.

FAQ

Does the result include the start day? What if both dates are the same?
This tool uses an "interval" convention throughout: neither the total days nor the working days include the start day. For example January 1 to January 2 is 1 day, and Monday to Friday is 4 days apart with 4 working days. When both dates are equal every figure is 0. If you prefer an inclusive count (for example holiday lengths), simply add 1 yourself.
Why are months and years approximate?
Because months and years vary in length (28–31 days and 365–366 days), the tool estimates using average lengths: 30.44 days per month and 365.25 days per year: which is fine for quick planning. For calendar-accurate months, cross-check month by month.
Does the calculation handle leap years?
Yes. The day count accumulates over the real calendar, so February 29 is included automatically; the year estimate uses the average year length of 365.25 days that already accounts for leap years, so slight differences between spans with and without a leap day are normal.
Do working days account for public holidays?
No. Only Monday to Friday are treated as working days; public holidays and make-up working weekends are not considered. For an exact count of business days, subtract the holidays in your location manually.

How to use

  1. Pick both dates

    Select a start date and an end date. Results update live, and if the order is reversed the tool swaps them automatically and shows a hint.

  2. Exclude weekends if needed

    Tick Exclude weekends to add a working-days figure. It counts Mondays through Fridays only and leaves Saturdays and Sundays out.

  3. Mind the counting rule

    Days use an interval convention that excludes the start day: January 1 to January 2 is 1 day. For an inclusive count such as a holiday length, add 1 yourself.

  4. Read weeks and estimates

    Weeks appear as whole weeks plus leftover days. Months and years are estimates based on 30.44 and 365.25 days, fine for rough planning.

  5. Copy the whole summary

    Click Copy result to grab days, weeks, month and year estimates and working days in one string. It pastes straight into schedules or leave requests.

About this tool

The date difference calculator accumulates over the real calendar, so leap days and uneven month lengths are handled automatically. February 29 counts toward the total. Days follow an interval convention that excludes the start day. Weeks are reported as whole weeks plus remaining days. Months and years are converted with average lengths of 30.44 and 365.25 days and labeled as estimates.

Use it for project schedules, rental or contract spans, holiday planning and probation countdowns. To see when a 90-day task starting March 1 finishes, adjust the end date until the total hits 90. To learn how many working days an interval consumes, tick the weekend exclusion and read the figure directly. Everything recomputes as you type and copies in one click.

How it works

Subtracting two dates cleanly maps each day onto a continuous integer known as the Julian Day Number. Leap years and uneven months then vanish into the mapping, and the difference is the day count. The integer formula published by Fliegel and Van Flandern in 1968 is still the textbook approach. Finance layers its own day-count conventions on top: 30/360, ACT/360 and ACT/ACT coexist. The same pair of dates accrues slightly different interest under each. This tool accumulates over the real calendar, the ACT/ACT equivalent. That is what makes it a handy reference when you audit another system. Check which convention the bank uses before comparing day counts.

The month and year figures are estimates. The mean month is 365.2425 ÷ 12 ≈ 30.436875 days, shown rounded to 30.44. The mean year is 365.25 days with leap years averaged in. They serve rough planning only. January 31 to March 1 is 29 calendar days, while the mean-month shortcut undercounts it. Working days assume five per week, about 71.4% of any span. Over long intervals, holidays and make-up workdays push real attendance lower still, so leave slack in the schedule. For cross-year checks trust the day count. When a figure goes into a contract, say whether the count is inclusive or exclusive, so the reader can re-verify it.

When to use it

  1. Counting down to a milestone

    Set the end date to the acceptance day and the day count becomes the runway left. Tick the weekend exclusion for working-day capacity. If it falls short of what the team needs, cut scope early.

  2. Rents and daily billing

    Daily-billed rent, parking and probation periods reconcile against the day count. The interval rule excludes the start day. Add one before disputing a landlord's count of 30 days occupied; that day is where most arguments start.

  3. Visa and insurance windows

    Walk the span from entry to expiry for every trip. Allowed stays are usually counted inclusively, one more than the interval figure here. Recompute with the extra day whenever a trip sits close to the cap.

Tips & tricks

  • Add 1 to the day count for inclusive spans such as trips. Identical dates yield 0 across the board.
  • Working days ignore public holidays and make-up weekend workdays. Adjust manually for your region.
  • Set the end date to a deadline and the day count doubles as remaining preparation time for planning.

Things to watch

  • Mean months are not calendars

    A month of 30.44 days estimates totals and cycles only. For spans straddling month ends, trust the day count instead. The estimate is deliberately smooth and will not match the calendar.

  • Working days skip holidays

    The weekend exclusion removes Saturdays and Sundays alone. Public holidays and make-up workdays stay outside the model. Adjust manually around the local holiday calendar before quoting attendance figures.

  • Leap years bend the year figure

    Years average 365.25 days, so a span with exactly one leap day rounds slightly high. A span without one rounds low. For contracts under four years, compare days ÷ 365 against the year figure.

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