Date Add / Subtract Calculator

Add or subtract years, months, weeks, days, hours, and minutes to or from any starting date to compute exact future or past target dates.

Why Use This Tool?

• Deadline Planning: Calculate a future deadline date by adding 90 days or 6 weeks to a starting date.
• Warranty & Expiration Dates: Calculate warranty expiration dates by adding 1 or 2 years to purchase dates.
• HR Notice Periods: Determine final working day by adding notice period days.

How to Use

1. Select Start Date and Action ("Add" or "Subtract").
2. Enter Years, Months, Weeks, or Days to add or subtract.
3. View resulting target date and day of the week.

Real Working Example

Input:

Start Date: March 15, 2026 | Action: Add | Duration: 90 Days

Output Result:

Resulting Date: Saturday, June 13, 2026 (90 Days Added)

Important Technical Details & Formulas

• JavaScript Date ISO Arithmetic: Handles leap years, month length variations, and year boundaries accurately.
• Includes Day of Week Output: Displays day of the week (Monday, Tuesday, etc.) for the target date.
• Client-Side Engine: Fast calculation in local browser memory.

Related Mathematics & Financial Tools

• Date Difference Calculator: Calculate days between dates.
• Age Calculator: Calculate age from date of birth.
• Business Days Calculator: Count working business days.