Date Calculator
Two modes in one tool. 'Add / Subtract' lets you start from a date and offset it by any combination of years, months, weeks, plain days, or business-only days — useful for figuring out a deadline, a contract end, or 100 days from today. 'Between' takes a start and end date and returns the exact difference (years / months / days), plus totals in days, weeks, months, and business days.
Result
Sun, Sep 20, 2026
2026-09-20
How to use
- Pick a mode: Add / Subtract or Between.
- Set the date(s) and any offsets you want.
- Read the resulting date or the breakdown between the two dates.
Frequently asked questions
- What counts as a business day?
- Monday through Friday. Public holidays aren't subtracted — they vary by country. For an exact deadline in your jurisdiction, double-check against the local holiday calendar.
- How are months handled?
- By calendar month. Adding 1 month to Jan 31 gives Mar 3 (because Feb has 28 days that year), then the day overflow rolls into the next month. This matches how most spreadsheets and SQL databases do month arithmetic.
- Why does 'years 0 months 11 days 30' show instead of '1 year'?
- The Between view always uses calendar components — full calendar years first, then remaining months, then remaining days. 11 months + 30 days is not a full year because the next month might be 31 days.
- Is the date stored?
- Only in your browser's local storage so the inputs survive a reload. Nothing is uploaded.
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