Date Addition Calculator
Add or subtract days, weeks, months, and years from any date — calendar-accurate. Find 100 days from hire date exactly — free, local, no signup.
How to Use the Date Addition Calculator
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Frequently Asked Questions
100 days from March 1?
June 9 (non-leap) — real month lengths apply, never 30-day approximations. Probation and warranty math stays exact.
Months variable length?
Yes — adding one month to January 31 lands February 28/29 (month-end clamping). The tool follows calendar convention, not fixed days.
Subtract too?
Negative offsets go backward — 90 days before today for lookback windows. Both directions, one tool.
Are dates uploaded?
No — math runs locally in your browser. Dates never leave your device.
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Last updated October 2026