Date Difference Calculator
Count elapsed calendar days or include both dates, with whole weeks and remaining days.
Last updated: November 4, 2026
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Quick summary: Count elapsed calendar days or include both dates, with whole weeks and remaining days.
Read the complete guide
Updated reference sections in this guide are in English.
Two useful ways to count days
Choose the start and end dates, then select a counting convention. Elapsed days counts the date boundaries between them: today to tomorrow is one day. Inclusive counting adds one so that both dates count as days in the interval: today through tomorrow is two days. The end date must be on or after the start date; the Swap dates button can reverse the entries.
Calendar dates instead of clock times
Inclusive days = elapsed days + 1
Whole weeks = floor(total days ÷ 7)
Remaining days = total days modulo 7
The form treats each input as a Gregorian calendar date and normalizes the calculation to date boundaries. It does not measure a stopwatch interval or infer a timezone. A daylight-saving transition therefore does not turn one calendar day into a fraction of a day.
Examples and boundary cases
One month that has 30 elapsed days
From October 1, 2026 to October 31, 2026 is 30 elapsed days, or 31 days when both dates are included. Thirty elapsed days split into 4 whole weeks and 2 remaining days.
Crossing a leap day
February 28, 2024 to March 1, 2024 spans 2 elapsed days. The same month and day combination in 2025 spans 1 elapsed day.
The same date twice
A start and end date that are identical gives 0 elapsed days or 1 inclusive day. Neither result is an error; they use different counting conventions.
Check this scenario in the calculator:
- Start date
- 2026-10-01
- End date
- 2026-10-31
- Counting convention
- Elapsed days — exclude the start date
Use the convention your task requires
A travel itinerary, a record of attendance and a notice period can count their first and last days differently. Select the convention that matches the rule you are using rather than assuming every date range is inclusive. Whole weeks in the result are groups of seven days, not the number of calendar weeks touched by the interval.
What is outside the calculation
Business days, weekends, public holidays and country-specific calendars are not excluded. Clock times, timezone offsets and legal deadline rules are not modeled. This tool uses the Gregorian calendar for all supported years, including historical dates before a country adopted that calendar. Dates must be valid and fall between years 0001 and 9999.
Date-counting questions
Does this count working days?
No. Saturday, Sunday and public holidays count like any other calendar day.
Why not divide local timestamps by 24 hours?
Local midnights can be separated by 23 or 25 hours around a clock change. Calendar counting avoids that mismatch.
Will reversing the dates return a negative number?
No. The form asks you to swap the dates so the displayed interval has a clear start and end.