Need to know what the date will be in 90 days? Or what date it was 6 weeks ago? Stop counting on a calendar and let our free Online Date Calculator do the work for you. Instantly add or subtract days, weeks, months, and years from any date, or find the exact duration between two dates.

How to Use Our Date Calculator

Our tool offers two distinct functions for all your date-related math needs.

How to Add or Subtract from a Date

1. Select a Start Date using the date picker.
2. Choose whether you want to Add or Subtract time.
3. Enter the numerical amount and select the unit (Days, Weeks, Months, or Years).
4. The new date will be calculated and displayed instantly in the results box.

How to Find the Duration Between Two Dates

1. In the second calculator, select a From date.
2. Select a To date.
3. The tool will immediately show you the total number of days between the two dates.

Common Examples

• Project Planning: If a project starts today and is estimated to take 12 weeks, use the "Add" function to find the exact completion date.
• Billing Cycles: If an invoice is due 30 days from the issue date, you can quickly find the due date.
• Personal Milestones: Find out how many days are left until your birthday or a vacation.
• Historical Reference: Calculate what the date was 5 years and 3 months ago.

The Challenges of Calculating Dates Manually

While adding a few days to a date seems simple, date calculations can get surprisingly complex. Manually accounting for these factors is tedious and prone to error:

• Varying Month Lengths: Months can have 28, 29, 30, or 31 days. Adding "1 month" from January 31st is very different from adding it from April 30th.
• Leap Years: The addition of February 29th every four years (with exceptions) can throw off long-term calculations if not handled correctly.
• Time Zones & Daylight Saving: While our calculator standardizes dates to avoid this, real-world programming often has to account for shifting time zones.

Our tool handles all these complexities for you by leveraging your browser's built-in JavaScript `Date` object. This object is specifically designed to correctly manage month lengths and leap years, ensuring you always get an accurate result without any manual counting.

Frequently Asked Questions (FAQ)

Q1: Does this calculator include the end date in the duration calculation?

No. When calculating the duration between two dates, our tool counts the number of full 24-hour periods. For example, the duration between today and tomorrow is "1 day." This is the standard way most people think about date differences.

Q2: How does the calculator handle adding a month to the 31st?

The calculator handles this logically. For example, if you add 1 month to January 31st, the result will be March 3rd (or March 2nd in a leap year), because February does not have 31 days. It correctly calculates the end of February and adds the remaining days to March.

Q3: Can I calculate the number of business days?

This is a simple date calculator and does not have the functionality to exclude weekends or public holidays. It calculates the total number of calendar days only.