hCalendar (short for HTML iCalendar) is a microformat standard for displaying a semantic (X)HTML representation of iCalendar-format calendar information about an event, on web pages, using HTML classes and rel attributes.
It allows parsing tools (for example other websites, or browser add-ons 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
(<a href="http://en.wikipedia.org/wiki/History_of_Wikipedia">more information</a>) </p>
hCalendar mark-up may be added using span HTML elements and the classes vevent, summary, dtstart (start date), dtend (end date), location and url:
<p class="vevent">
The <span class="summary">English Wikipedia was launched</span>
on 15 January 2001 with a party from
<abbr class="dtstart" title="2001-01-15T14:00:00+06:00">2pm</abbr>-
<abbr class="dtend" title="2001-01-15T16:00:00+06:00">4pm</abbr> at
<span class="location">Jimmy Wales' house</span>
(<a class="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 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. The newer h-event microformat therefore uses the HTML5 element time instead: <time class="dt-start" datetime="2013-06-30 12:00">30<sup>th</sup> June 2013, 12:00</time>
Geo
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.
Attributes
For a full list of attributes, see the hCalendar cheat-sheet.
Users
Notable organisations and other websites using hCalendar include:
Birmingham Town Hall and Symphony Hall
Google (in Google maps and in Search Engine Results Pages ) The Opera web browser website The Radio Times The University of Bath The University of Washington Upcoming.org Wikipedia Yahoo!, on Yahoo! Local