Date Calculator
Add or subtract days, weeks, months, or years from any date. Or find the exact number of days between two dates. Accounts for leap years and varying month lengths. Free and private.
How the Date Calculator Works
This calculator operates in two modes. In "Add/Subtract" mode, you enter a starting date and specify how many days, weeks, months, or years to add or subtract. The calculator produces the resulting date, accounting for leap years, month-length variations, and year boundaries. In "Difference" mode, you enter two dates and get the exact number of days, weeks, months, and years between them.
Date Calculation Methods
Adding Days: New Date = Start Date + N days
Adding Months: Move month forward by N, keep day (or clamp to month end)
Days Between: Total Days = |Date 2 − Date 1| in milliseconds / 86,400,000
- Leap years (Feb 29) are accounted for automatically
- Month addition clamps to last day if target month is shorter (e.g., Jan 31 + 1 month = Feb 28)
Example Calculations
Example 1: Add 90 Days from Today
Start: March 16, 2026 + 90 days = June 14, 2026
Example 2: Days Between Two Dates
From January 1, 2026 to December 31, 2026 = 364 days (52 weeks)
Example 3: Subtract 6 Months
Start: March 16, 2026 − 6 months = September 16, 2025
Common Uses for Date Calculations
Project deadlines, contract expiration dates, subscription renewals, notice periods, visa durations, payment due dates, warranty periods, pregnancy due dates, countdown to events, and age calculations. Any time you need to know "what date is X days/months from now" or "how many days until Y" — this is the tool.