References in the Grail Atlas catalog carrying the day complication.
Day-only complications (without date) are rare; the day indication usually pairs with date on a day-date or with a triple-calendar. The most cited day-only references are vintage Universal Genève Polerouter Day and certain Longines Conquest Heritage variants. Modern day-only is mostly an aesthetic choice on dress watches that did not want the date window.
An aperture, usually at twelve, showing the day of the week; a genuine calendar mechanism, because something has to index a seven-position disc once a day.
