Date Calculator
Calculates the difference in days between two dates, or the date a set number of days before or after a given date, in real time. Handy for checking contract periods or working out deadlines. Everything happens in your browser, and nothing you type is ever sent to a server. If you need to convert a date to the Japanese era calendar, check out the Japanese Era Converter as well.
🔒 Runs in your browser · Your data is never sent to a server
Difference between two dates
Date from a starting point
Notes
- This tool assumes the Gregorian calendar throughout. Dates before its adoption (pre-1582) may not match the calendar actually in use at the time.
- "Count both dates (inclusive)" counts both the start date and end date as full days — commonly used for contract periods or project durations.
- The supported date range is year 0001 through 9999.
Glossary
Inclusive counting
Counting both the start date and end date as full days. Many everyday date calculations (contract periods, project durations) count this way, while some legal contexts count only from the day after the start date. This tool lets you choose either.
Leap year
A year with an extra day (February 29), occurring every 4 years — except years divisible by 100, which are not leap years unless also divisible by 400 (e.g. 1900 is not a leap year, but 2000 is).
FAQ
When should I use "include the first day"?
Use it when both the start and end dates should count as full days, such as project schedules and contract periods. Many legal systems exclude the first day by default, so choose based on your rules.
Can it calculate business days excluding weekends and holidays?
No. It counts calendar days and does not account for weekends, public holidays or company closures.
How far back can I calculate?
Dates from year 0001 to 9999 are accepted. Calculations assume the Gregorian calendar, so dates before 1582 may not match the calendar actually in use then.
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