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Date Calculator

Calculate the difference between two dates, add or subtract days, count business days, and find exact age.

Calculator Tools Runs locally No data sent
date difference business days age calculator client-side only
Date Difference
Add / Subtract Days
Business Days Between Dates
Age Calculator

What is Date Calculator?

Date Calculator compares two dates in days, weeks, months, and years, adds or subtracts days from any date, calculates exact age from a birth date, and counts business days between dates. All calculations run locally in your browser and no data is uploaded.

How to Use Date Calculator

  1. To find the difference between two dates, enter a start date and an end date in the Date Difference section.
  2. To add or subtract time from a date, use the Add / Subtract section and enter the number of days to offset.
  3. To count business days between dates, use the Business Days section —weekends are excluded automatically.
  4. To calculate an age, enter a date of birth in the Age Calculator section and the result appears instantly.

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Understand Date Calculator ▾
Example
Input From: 2024-01-01 · To: 2024-12-31
Output 365 days · 52 weeks · 12 months · 0 years
Common Date Calculations
  • Project deadlines —calculate how many days remain until a milestone or delivery date.
  • Age calculation —determine exact age in years, months, and days from a date of birth.
  • Contract periods —find the end date of a 30-, 60-, or 90-day contract or notice period.
  • Invoice due dates —add net payment terms (Net 30, Net 60) to an invoice date.
  • Event planning —count down weeks and days to a wedding, reunion, or conference.
Why Use This Tool
  • Multiple calculation modes —date difference, add/subtract, business days, and age calculator in one place.
  • Multi-unit output —results shown in days, weeks, months, and years simultaneously.
  • Leap year aware —calculations correctly account for leap years.
  • Instant results —calculations update as soon as you change any date field.
  • Free and private —no data is uploaded; everything runs in your browser.
Frequently Asked Questions
Does the calculator include both start and end dates in the count?

By default the calculator counts the number of days between the two dates, not including the end date (like a programming range). If you need to include both dates, add one day to the result.

How are months calculated when months have different lengths?

Month differences are calculated by counting calendar months between the two dates. Partial months at the end are shown as remaining days.

Can I calculate working days (excluding weekends)?

Yes —the Business Days section counts only weekdays (Monday–Friday) between your two dates.

What date format should I enter?

Use the date picker or type dates in YYYY-MM-DD format. The tool uses your browser's locale to display dates in a readable format after calculation.