How to use Date Difference Calculator

1. Prepare the required inputs

Count calendar days and weeks between two dates with an optional inclusive end day. Use the units and options beside each field. Results update as inputs change; reset returns to example inputs.

Start date: calendar date
End date: calendar date
Include the end day: No — elapsed days / Yes — inclusive count

2. Try a worked example

1 January to 1 February 2026 is 31 elapsed calendar days; an inclusive count is 32.

3. Understand the calculation

Elapsed days = end calendar day − start calendar day. Inclusive count adds one. Whole weeks = floor(days ÷ 7).

4. Read the assumptions

Gregorian calendar dates, not elapsed hours. Daylight saving does not change the day count. The end must be on or after the start.

5. Check and compare results

Match entered values to their labels and units. Review output labels alongside the assumptions, then change one input at a time. A currency selector changes display labels without converting amounts. Use the available save or copy actions and retain the input values so the estimate can be reproduced.

6. Fix an invalid input

Complete required fields and respect the listed bounds. Check date order, age relationships and mode-specific requirements where relevant; the error message identifies invalid combinations. Reset to example inputs to recover. A valid calculation applies to its stated model and does not verify a real-world outcome.