Question 1

What is the ISO 8601 standard for week numbers?

Accepted Answer

The ISO 8601 standard is the international standard for week dates. In this system, weeks always start on a Monday. Week 1 of any year is the first week that contains a Thursday. This is the most common standard used in business across Europe and Asia.

Question 2

How do other week definitions work?

Accepted Answer

Some regions, particularly in North America, consider Sunday to be the start of the week. In these systems, Week 1 is simply the week that contains January 1st.

Question 3

Why does the ISO week year sometimes differ from the calendar year?

Accepted Answer

Because the ISO week year is based on which year the majority of the week's days fall in, the first few days of January can sometimes belong to the last week of the previous year, and the last few days of December can belong to the first week of the next year.

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