Publish by date

Pages, and even News, may be given a date on which the page will become visible or vanish.

Instead of using the calendar widget, one may type just english words e.g. “today”, “1 week” into the start- and end-date fields.
Entering “today” into start-date, and “1 week” into end-date will set the start-date on today and the end-date one week later. The end-date is count relative from start-date, i.e. “next monday” (start) and “1 month” (end) will result in next Monday's date as start-date, and next Monday plus one month as end-date.

See http://www.gnu.org/software/tar/manual/html_node/Relative-items-in-date-strings.html#SEC120