What is the ISO 8601 Week-Date?

ISO 8601 provides unambiguous numeric date/time representations and includes week dates, ordinal dates, time intervals and UTC-related formats.

How the calendar is structured

Week-numbering year, week number and weekday; week 1 is defined by ISO rules.

Where and why it is used

Region: Worldwide. Primary context: Business, logistics, software and international data interchange.

History and development

The system belongs to the Modern Technical layer of the archive. Its origin is summarized as International standard. CalculatorWiser separates historical reconstruction, religious observance, civil use, and modern technical standards so different systems are not treated as though they all work the same way.

Visual reference gallery

Conversion and accuracy notes

Some calendar systems can be converted deterministically with modern algorithms. Others depend on observation, local authority, historical reconstruction, or regional practice. CalculatorWiser marks those distinctions rather than presenting uncertain dates as exact.

Research trail

This entry is part of the research-backed World Calendar Archive. Primary research anchor for this entry: International Organization for Standardization.