Microformat

Microformat (or MF sometimes abbreviated μF) is a web-based approach to semantic mark-up which seeks to re-use existing HTML/XHTML tags to convey metadata and other attributes in web pages and other contexts that support (X)HTML, such as RSS.

This approach allows software to process information intended for end-users (such as contact information, geographic coordinates, calendar events, and the like) automatically.

hCalendar - a Calendar Event
details @ http://microformats.org/wiki/hcalendar

check also hCalendar creator the http://microformats.org/code/hcalendar/creator