Week numbers in software

The concept of week numbers is virtually unknown in large parts of the world, so most software does not display week numbers by default. Some software has no support for week numbers at all, and in some software support is hidden by obscure settings and parameters. However, with a few tricks it is often possible to get week numbers anyway, even if the application does not have native support for them.

Note that there are several week numbering schemes, so you need to select the right one. The most widespread scheme is the one used on this site. It is commenly known as ISO week numbers, sometimes also referred to as first four-day week or first Thursday.

These pages explain how to use ISO week numbers in various popular software applications and programming languages.