Days between two dates
Difference in days
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Date N days before / after
Resulting date
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How to use the date calculator
"How many days until that event?" "What weekday is 100 days after signing?" Counting dates on your fingers is error-prone. This tool finds the difference in days and the date N days before/after, complete with the weekday.
Two modes
For the difference, just enter start and end dates — handy for trip lengths or days left to a deadline. Tick "include the first day" to switch to a both-ends-inclusive count, like an event span. For N days before/after, enter a base date and a number to see the date and weekday.
Mind the counting method
Counting differs by context. A "3-day trip (Fri–Sun)" spans 3 days inclusive, but the "difference" from Friday to Sunday is 2 days. Toggle "include the first day" to match your use. Leap years and month boundaries are handled automatically.
Frequently asked questions
How are the days counted?+
The difference between two dates is computed on the Gregorian calendar.
By default it is end minus start; ticking "include the first day" counts one more (both ends inclusive).
By default it is end minus start; ticking "include the first day" counts one more (both ends inclusive).
How is the date N days later calculated?+
The number of days is added (N days after) or subtracted (N days before) from the base date.
Month, year and leap-year boundaries are handled automatically.
Month, year and leap-year boundaries are handled automatically.
Does it handle leap years?+
Yes. It follows the Gregorian leap-year rule: years divisible by 4 are leap years, except years divisible by 100 but not by 400.
How is the weekday determined?+
The weekday is computed from the date and shown in English. It is a standard Gregorian-calendar calculation.
Are the dates I enter stored?+
No. All calculation happens in your browser, and the dates you enter are never sent to or stored on a server.
Method
・Difference = (end − start) in days (+1 if the first day is included)
・N days before/after = base date ± days
・Calendar: Gregorian (ISO 8601), following the leap-year rule.
・Times and time zones are ignored; calculations use calendar days.
・Difference = (end − start) in days (+1 if the first day is included)
・N days before/after = base date ± days
・Calendar: Gregorian (ISO 8601), following the leap-year rule.
・Times and time zones are ignored; calculations use calendar days.
Please note
This site does not represent any organization and does not guarantee the accuracy of the results. Legal or contractual "counting from" rules (whether the first day is included) vary by agreement and jurisdiction. Confirm important dates with the source or the parties involved.
This site does not represent any organization and does not guarantee the accuracy of the results. Legal or contractual "counting from" rules (whether the first day is included) vary by agreement and jurisdiction. Confirm important dates with the source or the parties involved.