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Date Calculator

Add or subtract days from a date, or find the duration between two dates.

Mode

Inputs

Result

Resulting date
Jan 31, 2024
Wednesday · 2024-01-31

What is the Date Calculator?

A date calculator is a free online tool that adds or subtracts days, weeks, months and years from any starting date, and also calculates the exact duration between two dates in days, weeks, months and years.

Date Calculator formula

For date arithmetic, full calendar cycles are added or subtracted from the start date. Date difference = end date − start date, expressed in days; weeks = days ÷ 7, and years/months are derived from calendar-aware month-by-month counting so leap years and variable month lengths are handled correctly.

How to use the Date calculator

  1. 1Pick a mode: 'Add/Subtract' to shift a date, or 'Duration' to measure between two dates.
  2. 2Enter your start date (and end date, if in Duration mode).
  3. 3Choose the units to add or subtract (days, weeks, months or years) and enter the amount.
  4. 4Click Calculate to see the resulting date plus a breakdown of total days, weeks, months and years.
  5. 5Use the result to plan deadlines, leases, project milestones or countdowns.

Example calculation

Adding 90 days to 2024-01-01 gives 2024-03-31 (a leap year, so February has 29 days). The duration between 2023-03-14 and 2024-11-20 is 1 year, 8 months and 6 days, equal to 617 days or approximately 88 weeks.

Frequently asked questions

How do I add days to a date?
Enter the start date, choose 'Add', enter the number of days and click Calculate. Our calculator walks the calendar day-by-day so month lengths and leap years are handled correctly.
How many days are between two dates?
Switch to Duration mode, enter both dates and click Calculate. The result shows the exact difference in days, plus the equivalent in weeks, months and years.
Does the date calculator handle leap years?
Yes. We use real calendar arithmetic, so February 29 in leap years is counted correctly. For example, adding 1 year to 2024-02-29 returns 2025-02-28 because 2025 is not a leap year.
Can I subtract months from a date?
Yes. Pick 'Subtract', choose months, enter the amount and Calculate. The result rolls back the calendar month-by-month and adjusts the day if needed (e.g. March 31 − 1 month = February 28 or 29).
What is a business day calculator?
A business-day calculator counts only Monday–Friday and optionally skips public holidays. This tool counts calendar days; for business-day math, exclude weekends manually from the total.

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