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Date Calculator — Add, Subtract & Diff Dates (Business Days)

Add or subtract years, months, weeks, days, hours and minutes to a date — or compute the difference between two dates with business-day count.

Free No signup Client-side Privacy friendly Updated

Values may be negative to subtract.

Result

Pick a start date to begin.

Duration

Pick both dates to compare.

How to use

  1. 1 Pick a mode — Add / subtract a duration from a date, or compute the Difference between two dates.
  2. 2 In Add mode, type any positive or negative number into the Years / Months / Weeks / Days / Hours / Minutes fields.
  3. 3 In Difference mode, pick both dates and times. Calendar breakdown plus totals appear instantly.
  4. 4 Copy the ISO result with the Copy ISO button (Add mode).

Why use this tool

  • Day-of-month clamp — adding 1 month to Jan 31 gives Feb 28 or 29, not "Feb 31".
  • Calendar Y/M/D breakdown alongside totals — both views matter for different jobs.
  • Business-days counter excludes weekends (Mon–Fri).
  • No timezone surprises — calculations stay in your local zone.

Frequently asked questions

Does the business-days count exclude holidays?

No, it only excludes Saturdays and Sundays. Public holidays vary by country so we don't hard-code them — subtract holidays manually if needed.

Why does "1 year" not always equal 365 days?

Calendar arithmetic snaps to the same month / day, so the day count can be 365 or 366 depending on leap years. The Total days field shows the exact figure.

Need to convert the result into another timezone?

Use our Timezone Converter — paste the ISO output, then pick source and target zones.

How do I add hours across daylight saving?

Add Hours uses calendar time. Crossing a DST boundary will appear to "jump" by an hour. For instant arithmetic, use the Unix Timestamp Converter.

What is Date Calculator?

A Date Calculator is a tool that adds or subtracts years, months, weeks, days, hours, and minutes from a given date, or computes the difference between two dates. It runs in the browser and includes a business-day count, returning a resulting date or a duration broken down into calendar units.

Features

Add & subtract

Shift a date by any mix of years, months, weeks, days, hours, and minutes.

Date difference

Get the exact Y/M/D gap between two dates, plus total days.

Business days

Counts weekdays between two dates for working-day estimates.

100% private

Runs client-side — your dates never leave the browser.

Example

Input

2026-01-01  →  2026-12-31  (difference)

Output

0 years, 11 months, 30 days  (364 days total)

Common use cases

  1. 1

    Project deadlines

    Add a duration to a start date to find a milestone or due date.

  2. 2

    Count days to an event

    Find how many days (or working days) remain until a launch or trip.

  3. 3

    Age & tenure

    Compute an exact years/months/days span between two dates.

Summary

Zerethon's date calculator does two things in your browser: add or subtract years, months, weeks, days, hours, and minutes from a date, and compute the difference between two dates. Difference is reported as a years/months/days breakdown plus total days and business days, using calendar-aware arithmetic that clamps overflow (e.g. Jan 31 + 1 month → Feb 28). Nothing is uploaded.

Category
Creator
Pricing
Free
Privacy
Browser-based
Signup
Not required

References

Privacy

Your data never leaves your browser unless explicitly stated. Date Calculator runs entirely client-side — no server upload, no logging, no tracking of your input.

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