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.
Tips for Getting Accurate Results
For the most accurate results, use up-to-date numbers from official sources. Double-check your inputs before calculating — small errors in the starting values can lead to significantly different outputs. If you are comparing scenarios, keep all variables the same except the one you are testing. Save or screenshot your results for future reference. This calculator uses standard formulas and is designed to give you a reliable quick estimate, though professional advice may be needed for complex situations.
Frequently Asked Questions
How do I calculate a date 90 days from now?
Select "Add/Subtract from a date" mode, enter today's date, choose "Add", enter 90, and select "Days". The calculator gives you the exact date 90 days from your start date.
Does this account for leap years?
Yes. The calculator uses the actual calendar system, so February 29 in leap years and all month-length variations are automatically handled.
What happens when adding months to the 31st?
If the resulting month has fewer days (e.g., adding 1 month to January 31), the date clamps to the last day of that month (February 28 or 29). This is standard calendar behavior.
Can I calculate business days instead of calendar days?
This calculator uses calendar days. For business days (excluding weekends), use our Business Day Calculator.
How do I find how many days until a specific date?
Switch to "Days between two dates" mode, enter today as the start date and your target as the end date. The result shows the exact number of days.