日付計算ツール
2つの日付の差を計算し、日付の加算・減算、営業日の計算ができます。
What Is the Date Calculator?
The date calculator has three modes. Date Difference computes the gap between two dates in days, weeks, months, years, hours, and business days. Add / Subtract adds or subtracts years, months, and days from a starting date. Business Days finds the date that is exactly N business days (Mon–Fri) from a starting date, or counts the business days between two dates.
How to Use the Date Calculator
- Select the Date Difference tab and enter a start and end date to see the gap in multiple units.
- Use the Add / Subtract tab to find a future or past date by entering positive or negative years, months, and days.
- Use the Business Days tab to skip weekends: enter a start date and the number of business days to advance (or go back with a negative number).
Features
- Date difference in days, weeks, months, years, and hours
- Business days count (Monday–Friday, no weekends)
- Add or subtract years, months, and days from any date
- Find a date N business days from a start date
- Displays the day of the week for all result dates
- Swap start and end date with one click
FAQ
How is the date difference calculated?
The total number of days is calculated from the exact millisecond difference between the two dates. The years/months/days breakdown follows calendar arithmetic, adjusting for varying month lengths.
What counts as a business day?
Business days are Monday through Friday. Saturdays and Sundays are excluded. Public holidays are not currently taken into account.
Can I subtract days or months?
Yes. In the Add/Subtract tab, enter negative numbers to go back in time. For example, entering -30 days subtracts 30 days from the start date.