週番号計算機とは？

無料のオンライン週番号計算機。日付に対応する ISO 週番号と週数の差を計算。

ISO week numbers are the standard way to organize and communicate dates in business, manufacturing, and project management contexts. Week Number Calculator takes any date and instantly provides its ISO 8601 week number, ISO year, day of year, quarter, and other calendar context that helps with scheduling and planning.

The ISO 8601 week numbering system defines week 1 as the week containing the first Thursday of the year. Weeks start on Monday, and each week belongs to the year that contains its Thursday. This means that the first few days of January can sometimes belong to week 52 or 53 of the previous year, and the last few days of December can belong to week 1 of the next year.

The tool provides: ISO week number (1-53) with ISO year, day of year count with total days in that year, quarter number (1-4) with quarter date range, days remaining in the year, leap year detection, weekday name, and total weeks in the year. An interactive monthly calendar highlights the selected date for visual context.

Manufacturing schedules use week numbers for production planning. Academic institutions use them for term scheduling. Payroll departments use them for biweekly pay cycles. ISO 8601 compliance ensures that week numbers are consistent regardless of country or industry.