Template:When
From Organic Design wiki
This template is not actually used, the #when parser-function is used to add time information to articles. Just add a single parameter which can be arbitrarily formatted time information, for example: {{#when:2009/4/24}} - best to do dates backwards like this otherwise it tries to use some weird American format
{{#when:24 apr 2009}}
{{#when:24 apr, 4:30pm}} - current year is used here since not specified
The function expands to a set of category links to categorise the article into year, month, day-of-month, full-weekday-name and time (24 hour HH:MM:SS format). Articles exhibiting time can then be matched with a DPL query, for example:
{{#dpl:category=2006|category=April}}