Plugins - Element Criteria Model. Can I return only entries with a updated date in the last 7 days?
I'm not sure if there's some other Craft helpers / static variables that you could use, but this technique works. Create a DateTime object without the param set to get the current time, modify it and format it for use in the query like so:

$date = new DateTime();
$date-&gt;modify('-7 days');

// Format datetime for use in query
$timezone = new \DateTimeZone(DateTime::UTC);
$date = $date-&gt;format(DateTime::MYSQL_DATETIME, $timezone);

$criteria-&gt;dateUpdated = '&gt; '.$date;