It allows parsing tools (for example other websites, or browser add-ons[1] like Firefox's Operator extension) to extract the details of the event, and display them using some other website, index or search them, or to load them into a calendar or diary program, for instance. Multiple instances can be displayed as timelines.
Example
Consider this semi-fictional example:
The English Wikipedia was launched
on 15 January 2001 with a party from
2-4pm at
Jimmy Wales' house
(more information).
The HTML mark-up might be:
<p>
The English Wikipedia was launched
on 15 January 2001 with a party from
2-4pm at
Jimmy Wales' house
(<ahref="http://en.wikipedia.org/wiki/History_of_Wikipedia">more information</a>)
</p>
hCalendar mark-up may be added using spanHTML elements and the classesvevent, summary, dtstart (start date), dtend (end date), location and url:
<pclass="vevent">
The <spanclass="summary">English Wikipedia was launched</span>
on 15 January 2001 with a party from
<abbrclass="dtstart"title="2001-01-15T14:00:00+06:00">2pm</abbr>-
<abbrclass="dtend"title="2001-01-15T16:00:00+06:00">4pm</abbr> at
<spanclass="location">Jimmy Wales' house</span>
(<aclass="url"href="http://en.wikipedia.org/wiki/History_of_Wikipedia">more information</a>)
</p>
Note the use of the abbr element to contain the machine readable, ISO8601, date-time format for the start and end times.
Accessibility concerns
Concerns have been expressed[2] that, where it occurs, the use of the abbr element (using the so-called abbr-design-pattern) in the above manner causes accessibility problems, not least for users of screen readers and aural browsers.[3] The newer h-event microformat therefore uses the HTML5 element time instead:
The Geo microformat is a part of the hCalendar specification, and is often used to include the coordinates of the event's location within an hCalendar.