APEX

The code below uses page items to set filters on an IG. I can get the regular text string to add the filter, however I can't get the date filter to add. It adds a blank filter. Is there something I need to do to the date to create the date filter

var grid = apex.region("dd2663");
var filterSite = apex.item("P8_SITE_ID").getValue();
var filterStartDate = apex.item("P8_START_DATE").getValue();
var filterEndDate = apex.item("P8_END_DATE").getValue();
var filters = grid.call("getFilters");
if (filters.length >= 1) {
   for (var i in filters) {
       grid.call("deleteFilter", filters[i].id);
   }
}
if (filterSite && filterStartDate) {
   console.log("Filter on Site and Start Date");
   grid.widget().interactiveGrid("addFilter",{
       type: 'column',
       columnType: 'column',
       columnName: 'A450_SITE_ID',
       value: filterSite,
       operator: 'EQ',
       isCaseSensitive: false
   });
   console.log(filterStartDate);
   grid.widget().interactiveGrid("addFilter",{
       type: 'column',
       columnType: 'column',
       columnName: 'A450_BUS_DATE',
       value: filterStartDate,
       operator: 'GREATER_THAN_EQUAL',
       isCaseSensitive: false
   });
   grid.refresh();
} else if (filterSite) {
   console.log("Filter on Site");
   grid.widget().interactiveGrid("addFilter",{
       type: 'column',
       columnType: 'column',
       columnName: 'A450_SITE_ID',
       value: filterSite,
       operator: 'EQ',
       isCaseSensitive: false
   });
   grid.refresh();
}