Date Calculator (Add / Subtract Days)
Add or subtract days, weeks, months, or years from a date.
Date Calculator (Add / Subtract Days)
Add or subtract days, weeks, months, or years to or from any starting date with calendar-aware leap year and month-end rules.
Adding 30 days to October 12, 2026 results in November 11, 2026 (Wednesday).
What is a Date Calculator and How Does It Work?
The Date Calculator allows you to add or subtract days, weeks, months, or years to or from any starting date. It uses calendar-aware rules so that adding 1 month to January 31 correctly yields February 28 (or Feb 29 in leap years).
Adding 30 full days to Jan 1 results in Jan 31.
February 2026 has 28 days, so Jan 31 clamps to Feb 28.
Common Real-World Use Cases
Add a number of business days or weeks to a start date to find a realistic project deadline.
Calculate renewal dates by adding a validity period (e.g. 10 years) to an issue date.
Add a supply duration to a fill date to determine the next prescription refill date.
Subtract or add a required notice period (e.g. 30 or 60 days) from a target date for contracts or leases.
- 1Choose a Starting Date (or click Today).
- 2Select Operation (Add or Subtract).
- 3Enter the Amount (e.g. 30, 90, 180).
- 4Select the Unit (Days, Weeks, Months, Years) to calculate the resulting target date.
- •When adding months, if the target month has fewer days than the starting day (e.g. Jan 31 + 1 month), the result is automatically clamped to the last day of that month.
- •Use this tool for project timelines, passport renewals, prescription refills, and notice periods.
Frequently Asked Questions
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