The two pages This Week's Events and Next Week's Events list both seminars and conferences during a specified week. For seminars, this is built-in, based on their entry in gcal. For conferences, it's best to announce it via a news item in gcal (by tagging it with #news), and to also tag the announcement with the hashtag #dir corresponding to the conference folder /www/math/events/conferences/dir. Then it will appear in the above two pages on the appropriate dates.
For example, the menu item
Graduate Student Conference in Algebra, Geometry, and Topology under
Conferences corresponds to the folder /www/math/events/conferences/gscagt, so the announcement for this event should be tagged #news and #gscagt (for more information click
Adding News Items). The announcement then appears on these two pages on the appropriate dates.