Add / Subtract Days Calculator
Add or subtract days, weeks, months, or years from any date.
Date & Time
Add / Subtract Days Calculator
Generated on April 24, 2026
?What is the Add / Subtract Days Calculator?
This calculator lets you add or subtract any number of days, weeks, months, or years from a starting date — answering everyday questions like 'What date is 90 days from today?', '30 days before Christmas?', or 'My warranty expires 1 year after purchase — what's the date?'. It is essential for scheduling, meeting deadlines, planning events, verifying contract timelines, and any scenario where a specific date must be computed from a base date plus a duration. The tool handles calendar edge cases automatically, including month-end rollovers and leap years.
The Formula
Days and weeks add linearly — 10 days added to April 20 gives April 30, and 2 weeks added gives May 4. Months and years respect calendar boundaries: adding 1 month to January 31 gives February 28 (or 29 in a leap year), not March 3. Leap-year February 29 + 1 year correctly falls back to February 28 in non-leap years. This behavior matches what humans naturally expect when they say 'one month from today' — not 30 days exactly, but the same day number in the next month.
Practical Examples
Today + 90 days gives the typical end-of-notice-period date for a three-month notice clause — useful for resignation planning.
Invoice due date often equals the invoice date + 30 days ('Net 30') — the standard for commercial invoicing worldwide.
Warranty expiry: the purchase date + 1 year (or 2 years for consumer electronics in many countries) — useful for claim planning.
Legal and court deadlines: a filing deadline of 21 days from notice receipt is instantly computable.
Pregnancy due date: last menstrual period + 280 days (40 weeks) gives the standard due date estimate.
Subscription renewal: the signup date + 12 months tells you when a one-year subscription will auto-renew.