About

Your browser downloads the site's pages, styles and scripts from a CDN, so the hosting provider sees those requests. The calculations run in your browser; the values you enter stay in the page and are not uploaded.

The aim is to make date calculations easy to check. When the site cannot account for a holiday or an institution's convention, the page explains that limit rather than presenting the result as certain.

See the methodology page for calculation rules and how they are checked.