When you use the built-in jQuery UI datepicker in your APEX page, you choose from a number of different format masks...but something with "week" is not one of them. And guess what I needed for recent project... But, the good news is, you can (rather easy) use the jQuery framework to tweak the result that's returned from the datepicker. Just create a Dynamic Action that fires on load of the page, and add these line of Javascript: //Show the week number as the first column $( ".datepicker" ).datepicker( "option", "showWeek", true ); //Set Monday as the first day of the week $( ".datepicker" ).datepicker( "option", "firstDay", 1 ); //Return yyyy-ww instead of the actual date $(".datepicker").datepicker("option", "onSelect", function(value, date) { var week=$.datepicker.iso8601Week ( new Date(date.selectedYear, ...