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D-day Calculator

Calculate date differences, milestones, and more in one place.

Inputs

Calculate days remaining or elapsed between two dates.

This option affects duration only. The D-day display is unchanged.
Your dates are not sent to or stored on the server.
CALCULATION RESULT

How to use

  1. 01

    Set both dates

    Enter the starting and comparison dates. Check the actual calendar dates rather than relying only on a D-day label.

  2. 02

    Choose the counting convention

    Decide whether to include the starting day, then calculate the difference.

  3. 03

    Read the direction and count

    Distinguish days remaining from days elapsed. Keep the date pair with the result.

Frequently asked questions

Are weekends excluded?

No. This is a calendar-day calculation, not a working-day or public-holiday calculator.

Why can the answer differ by one day?

Including the starting day changes the counting convention. Use the same convention when comparing results.

Does time of day matter?

Inputs are calendar dates. This tool does not calculate hours, time zones or daylight-saving transitions.

Important information

Tool files and calculation inputs are processed in your browser, without uploading them to a processing server.

Keep original files and reopen downloaded results before replacing a working copy.

Tested example

Input and settings

2024-01-01 to 2024-01-11, excluding the starting day

Observed result

A 10-day difference

What to check

Changing the starting-day convention can change the result by one day.

Examples use synthetic, non-personal test material. Results apply to the inputs and settings shown; different files and devices can produce different sizes, timing and appearance.