Is my data sent to a server?

No. All date calculations run entirely in your browser using JavaScript's built-in date functions.

Does the tool account for leap years?

Yes. The JavaScript Date API handles leap years correctly in all difference and addition calculations.

Can I calculate business days (excluding weekends)?

Yes. Enable the business days option to exclude Saturdays and Sundays from day-count calculations.

Can I add months or years to a date, not just days?

Yes. The add/subtract mode supports days, weeks, months, and years.

Date calculator

Date calculator is a browser-based time tool with four modes: find days between two dates, add or subtract time from a date, calculate exact age, or count down to a future event. All calculations use your browser's native date support.

Start dateEnd date

End date is same day

0 days

Weeks

0w 0d

Approx months

0.0

Approx years

0.00

Today: May 25, 2026

Calculation modes

Direct links for each date calculation type.

Days between dates

Calculate exactly how many days, weeks, months, and years are between two dates. Instant, in your browser.

Add or subtract days from a date

Find the date that is N days before or after any given date. Free in-browser date calculator.

Age calculator

Calculate your exact age in years, months, and days from your date of birth. Free, in-browser age calculator.

Days until a date

Count down to any future date. See exactly how many days and weeks remain. Free, in-browser countdown calculator.

How to calculate the difference between dates

Enter the start date and end date using the date pickers.
The tool calculates the difference in days, weeks, months, and years.
Alternatively, enter a date and add or subtract a number of days to find a future or past date.
All calculations happen instantly in your browser.

Common uses

Calculating how many days until an event or deadline
Working out someone's age or how long ago something happened, use Unix timestamp converter when dealing with epoch-based dates from APIs
Adding business days to a date for scheduling or contract deadlines. The percentage calculator helps when you need to express time elapsed as a fraction

Technical specification

Algorithm or formula: Difference mode subtracts two epoch millisecond values then converts to days, weeks, months, and years. Add or subtract mode mutates a Date with setDate, setMonth, or setFullYear. Business-day mode iterates day-by-day and skips Saturdays and Sundays.
Browser API or library: Native JavaScript Date. No external library.
Input limits: Any date the Date object accepts. Practical range covers any historical or near-future application.
Output: Difference in days, weeks, months, and years; new dates from add or subtract; weekday name; ISO date string.
Known limitations: Holidays are not detected (business days exclude only Saturdays and Sundays). Time-zone-sensitive calculations use the browser's local time zone.

Frequently asked questions

Is my data sent to a server?: No. All date calculations run entirely in your browser using JavaScript's built-in date functions.
Does the tool account for leap years?: Yes. The JavaScript Date API handles leap years correctly in all difference and addition calculations.
Can I calculate business days (excluding weekends)?: Yes. Enable the business days option to exclude Saturdays and Sundays from day-count calculations.
Can I add months or years to a date, not just days?: Yes. The add/subtract mode supports days, weeks, months, and years.

Reviewed and tested May 25, 2026.