日数の加算・減算

共有リンク

はじめに

Add or Subtract Days — Jump forward or back a set number of days from any date. Enter Start date, Days, Operation to get an instant, accurate result.

計算式

Result date = start date ± number of days, using real calendar-day arithmetic.

ステップごとの説明

Enter the Start date.
Enter the Days.
Enter the Operation.
Click Calculate to see your result instantly.

実例

Example: With Start date = 2026-10-09, Days = 30, Operation = +, the Add or Subtract Days gives Result Date: 2026-11-08.

よくある質問

Does this handle month/year boundaries correctly?

Yes, it's calculated using real calendar arithmetic, not a fixed 30-day month assumption.

Can I subtract a large number of days?

Yes, any number of days forward or backward works.

What inputs does the Add or Subtract Days need?

You'll need to provide: Start date, Days, Operation. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.

How accurate is the Add or Subtract Days?

The Add or Subtract Days applies the formula exactly as calculated — Result date = start date ± number of days, using real calendar-day arithmetic. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.

Is the Add or Subtract Days free to use?

Yes, the Add or Subtract Days is completely free, requires no signup, and runs instantly in your browser.