What week is it?

How ISO week numbers work

Under ISO 8601, weeks run Monday to Sunday, and week 1 is the week containing the year's first Thursday (equivalently, the week of 4 January). That means up to three days of early January can belong to the previous year's final week (1 January can be in week 52 or 53), and years have either 52 or 53 weeks.

Beware: the US convention (weeks start Sunday, week 1 contains 1 January) gives different numbers, which is why "week 32" can mean different things in different companies. When it matters, say "ISO week 32" and everyone can check a date. Planning that week's meeting across offices? Use the planner.