http://www.w3.org/1999/XSL/Transform

c.cacheUntil (until : datetime) : void

The function cacheUntil creates a dependency to a specific moment in time. The currently computed item will be invalidated at this specific moment. 

Time dependencies are additional dependencies. The current computation may still be invalidated through other data modifications.

<xsl:value-of select="c.cacheUntil('2007-01-01T12:00:00.0000000+02:00')" />
Create a time dependency to January 1st, 2007 at 12 AM.

The same function can be expressed as an xml tag:

<c.cache until="2007-01-01T12:00:00.0000000+02:00" />