For the purposes of determining when a Web page is born, we look at the time we first access a document; not the document's Last-Modified date. This means that if you create a page at 10:00 with a max-age of 1 hour, but nobody requests it until 10:04, it will expire at 11:04 instead of 11:00. If you want to be incredibly strict about when your Web page expires, use an Expires header instead of a max-age value. But this can often be problematic—see Using Expires headers.

Suppose that later, a different user requests that same document from your channel. Your M-Business Sync Server knows it has that page locally on its hard drive. The first thing it will do is calculate the page's age. The local time is 19:40:17 GMT, and your page was born on 17:28:02, so the page's age is 2:12:15, or 7935 seconds old.