Date Add/Subtract Calculator
Add or subtract days, weeks, months, or years from any date.
Overview
Adding a period to a date is unambiguous in days and ambiguous in months. Thirty days after 31 January is 2 March in a common year; one month after 31 January is undefined until a rule fixes it. The near-universal convention clamps to the last valid day of the target month, so 31 January plus one month resolves to 28 February, or 29 February in a leap year.
Quick Presets
Result Date
Day of Week
ISO Format
Days from Today
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How to Use
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Enter your values
Type your numbers into the Date Add/Subtract Calculator input fields.
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Adjust the options
Choose the units, method, or region that fits your situation, or apply a quick preset.
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Read the result instantly
The result updates as you type — no submit button, and nothing is sent to a server.
About
The clamping rule makes month arithmetic non-reversible. Adding one month to 31 January gives 28 February, but subtracting one month from 28 February gives 28 January rather than the original date. Anyone computing a rolling schedule applies the offset to the original anchor date each time rather than chaining increments, which would otherwise drift earlier every month.
Business-day arithmetic adds a further layer, skipping weekends and public holidays, which is why a payment due in thirty days and one due in thirty business days fall roughly six weeks apart.