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Date & Productivity Tools

Date Calculator

Add or subtract years, months, weeks and days, with explicit month-end rules and source/result calendar previews.

Your content stays on your device Free, with no account
Plan a date. See every calendar step.Local calculation · no uploads

Starting date & offset

Today uses your device’s local date. The calculation itself uses calendar dates without clock times.

Enter nonnegative whole amounts. Exact fields accept the full supported range; quick sliders disable when they cannot represent the value.

Calculation order

First apply years × 12 + months as one calendar-month shift. Then apply weeks × 7 + days. January 31 + 1 month + 1 day in 2024 becomes February 29, then March 1.

Dates from 0001-01-01 through 9999-12-31. No business-day, holiday or time-zone assumptions.

YOUR DATE CALCULATION

Choose a starting date to begin.

A FEW SIMPLE STEPS

How to use Date Calculator

  1. Choose a starting date, use your device’s local Today date or try the example.
  2. Choose Add or Subtract and enter nonnegative whole years, months, weeks and days. Sliders provide quick adjustments; exact fields accept wider ranges.
  3. Choose whether a missing day in the target month should clamp to month end or produce an error. Years/months apply together before weeks/days.
  4. Review the result date, weekday, source/result calendars and intermediate step. Copy the date or download the calculation report.
PRIVATE BY DESIGN

Why use this tool?

Your dates and offsets are processed entirely on your device. There is no upload, account, external calendar service or input history. Date-only arithmetic avoids hidden time-zone and daylight-saving assumptions.

Tool inputs stay in your browser. Only your theme preference is saved on this device.

A few things worth knowing

In what order are the offsets applied?

Years and months are combined into one signed calendar-month shift from the original date. Then weeks × 7 + days are applied as calendar days. For example, 2024-01-31 plus one month and one day becomes 2024-02-29, then 2024-03-01. This differs from applying each year/month sequentially with separate clamps.

What happens on the 29th, 30th or 31st?

When the original day is unavailable in the target month, Clamp uses its final day or Reject reports an error. A month shift does not preserve an end-of-month rule: April 30 plus one month becomes May 30. Clamping can make Add and Subtract non-inverse operations.

Are weekends, holidays or daylight-saving changes included?

Every week is seven calendar days; weekends and holidays count normally. The tool uses Gregorian dates without clock times, zones or daylight-saving conversions. Use a separate business-day workflow for workdays, or Time Zone Converter for clock-time conversions.

What ranges and inputs are accepted?

Valid Gregorian dates from 0001-01-01 through 9999-12-31. Years 0–9998, months 0–119987, weeks 0–521722 and days 0–3652058, with both the intermediate month step and final result required to stay within the supported date range. All amounts must be nonnegative whole numbers. Empty or invalid amounts reject; choose Add/Subtract for direction.

Does Today or a report send my date anywhere?

No. Today reads your device’s current local calendar date. Calculation and preview stay in the browser. The date is copied or a TXT report downloaded only when you choose that action; those external copies remain under your control.

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