Date Difference Calculator
About the Date Difference Calculator
Count the exact amount of time between two dates — in total days, weeks, and approximate months. Use it for project deadlines, notice periods, holiday planning, contract terms, or any "how many days until / since" question. It works entirely offline in your browser, so the dates you enter stay on your device.
This tool works in your browser: the files and text you use are processed on your device and are not uploaded.
How to use it
- Pick a start date and an end date.
- Press to calculate the difference.
- Read the gap as total days, its equivalent in weeks, and an approximate number of months.
Frequently asked questions
How is the difference between two dates worked out?
The tool takes the absolute gap between the two dates in days, so the order you enter them does not matter. Weeks are that day count ÷ 7, and months are approximated as days ÷ 30.43 (the average month length across a year).
Why are the months approximate?
Calendar months range from 28 to 31 days, so any single "months" figure from a raw day count is an estimate. Using the average 30.43-day month gives a close, consistent value; rely on the total-days figure when you need an exact answer.
Does the count include both the start and end date?
It measures the span between the two dates. If you need to count both endpoints inclusively (for example billing days), add one to the total-days result.
Can I measure a difference across leap years?
Yes — because the tool compares the real calendar dates, any February 29ths in the range are already included in the day total.