Date & Business Days Calculator
Calculate date differences, add or subtract time, and count business days.
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How to use it
- Mode 1 counts the days between two dates (leap years handled automatically).
- Mode 2 adds or subtracts years, months, weeks and days — month-end dates are clamped sensibly.
- Mode 3 counts business days between the dates of mode 1, skipping weekends and your holiday list.
- Negative day values work: adding −30 days moves the date backward.
About this tool
Three modes: the number of days between two dates, add or subtract days/weeks/months/years from a date, and business-day counting that skips weekends with an optional holiday exclusion list. Results show both calendar and working-day totals so plans are realistic.
Your input never leaves the browser: this tool works entirely offline once the page has loaded.
Frequently asked questions
How are business days defined?
Monday to Friday, excluding Saturday, Sunday and any dates you list as holidays. A holiday that falls on a weekend is not counted twice.
What happens when I add a month to January 31st?
The day is clamped to the target month's end: January 31 + 1 month = February 28 (29 in leap years), not March 3rd.