Days Between Dates Calculator
Use your own numbers after reviewing the formula and worked example.
Quick answer
Date difference measures elapsed calendar days, while inclusive counting may count one or both endpoints.
Formula or method
Keep units, percentages and time periods consistent. The formula is useful as a transparent check on the calculator result and helps explain why changing one input changes the answer.
Step-by-step
- Put dates on the same calendar basis.
- Subtract earlier from later.
- Decide whether endpoints count.
- Use business-day rules separately when required.
Worked example
January 1 to January 2 is one elapsed day; counting both dates inclusively gives two calendar dates.
How to interpret the result
Deadline rules can define counting differently, so plain elapsed days may not match a legal or contractual deadline rule.
When the answer is used for a purchase, loan, payroll decision, construction order, school grade, health estimate or other real-world choice, verify the assumptions that matter in that context. Accurate arithmetic still depends on accurate inputs.
Common mistakes
- Mixing inclusive and exclusive counting.
- Using business days when calendar days are required.
- Ignoring time zones for exact timestamps.
Frequently asked questions
Does start date count?
It depends on the rule.
Do weekends count?
Yes in ordinary calendar-day differences.
Are leap years handled?
A proper date calculation accounts for February 29.