Date Calculator
Three modes in one tool: add to a date, subtract from a date, or calculate the difference between two dates. Optional business-days-only mode skips weekends.
All calculations run in your browser. Nothing is uploaded.
How to use this date calculator
- Pick a mode: Add, Subtract or Date difference.
- Set the start date (use 'Today' for the current date).
- Enter the offset in years, months, weeks and days — or pick a second date for difference mode.
- Toggle Business days only to skip weekends in the calculation.
- Read the result with weekday, ISO week and day of year, and copy if needed.
Frequently asked questions
How is 'business days' calculated?
Saturday and Sunday are skipped. The tool advances or counts only Monday through Friday. Public holidays are not removed — for accurate workday counts in your country, subtract them manually.
What happens when I add months that don't have the same day?
If the start day doesn't exist in the result month (e.g. January 31 + 1 month), it's clamped to the last day of that month (February 28 or 29).
How is this different from Days Between Dates?
Days Between Dates calculates only the difference between two given dates. Date Calculator also lets you add or subtract a duration from a single date and gives Y/M/D breakdowns.
Why is 'Jan 31 + 1 month' showing Feb 28 instead of an error?
Different libraries make different choices when the target month doesn't have the day. This tool clamps to the last day of the target month (Jan 31 + 1m = Feb 28 or 29 in leap years). Some libraries roll forward (Mar 3). For accounting workflows where consistency matters, always 'add months' from the same anchor date rather than chaining month-additions.