Ok, try this approach:
JSConfig('filter', [TUniFilterDBGridColumn(Column).Filter], Column.JSColumn);
JSConfigObject('filter', 'fields', [JSStatement('{lt: { text: "Before!" }, gt: { text: "After!"}, eq: { text: "On!"}}')], Column.JSColumn); //add this...
JSConfig('filter', [JSStatement('{type: "date", fields: {lt: { text: "Before!" }, gt: { text: "After!"}, eq: { text: "On!"}}}')], Column.JSColumn);