# Date Calculator Workspace

> Date calculator: add or subtract days from any date, find the difference between two dates, and get the weekday result. Free, private, runs in your browser.

- **Canonical URL:** https://boringtoolskit.com/date-calculator-workspace/
- **Category:** Time & Work
- **Evidence level:** authored-methodology
- **Reviewed:** July 2026
- **Last verified:** 2026-09-20
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

Difference mode converts valid date-only values to UTC day numbers and subtracts them; inclusive mode adds the appropriate boundary day. Add/subtract mode applies years and months with month-end clamping, then applies weeks and days as whole 24-hour UTC date increments.

## Worked example

From February 28, 2024 to March 1, 2024 is two elapsed days, or three dates when both boundaries are counted. Adding one month to January 31, 2024 clamps to February 29, 2024.

## Assumptions

- Inputs are calendar dates without time-of-day or time-zone offsets.
- Monday–Friday counts exclude Saturdays and Sundays but do not infer public holidays.
- When a target month lacks the starting day, month arithmetic clamps to the final valid day.

## Common questions

### Why use UTC date arithmetic?

Date-only UTC arithmetic prevents daylight-saving clock changes from turning a calendar day into 23 or 25 hours.

### Are holidays excluded from weekday counts?

No. The calculator counts Monday through Friday only and does not claim a holiday calendar.

### What happens to January 31 plus one month?

If the target month lacks that day, the result is clamped to the target month’s final valid date.

## Related tools

- /date-difference-calculator/
- /business-days-calculator/
- /age-calculator/

## Sources

- [ECMAScript Date Objects](https://tc39.es/ecma262/multipage/numbers-and-dates.html#sec-date-objects)

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