Fix adding a time in legacy date picker (#49121)

* Fix adding a time in legacy date picker

* Fix the test

frontend/src/metabase/admin/datamodel/components/filters/pickers/DatePicker/DatePicker.unit.spec.tsx

@@ -240,9 +240,9 @@ describe("DatePicker", () => {
 
     describe("Specific Dates", () => {
       const singleDateOperators = [
-        ["=", "on"],
-        ["<", "before"],
-        [">", "after"],
+        ["=", "On"],
+        ["<", "Before"],
+        [">", "After"],
       ];
 
       singleDateOperators.forEach(([operator, description]) => {
@@ -265,6 +265,21 @@ describe("DatePicker", () => {
             "2020-05-21",
           ]);
         });
+
+        it(`can add time to a specific ${description} date filter`, async () => {
+          const filter = createDateFilter(operator, "2020-05-01");
+          const onChange = jest.fn();
+          render(
+            <DatePickerStateWrapper filter={filter} onChange={onChange} />,
+          );
+
+          await userEvent.click(screen.getByText("Add a time"));
+          expect(onChange.mock.lastCall[0]).toStrictEqual([
+            operator,
+            CREATED_AT_FIELD,
+            "2020-05-01T12:30:00",
+          ]);
+        });
       });
 
       it("can set a between date filter", async () => {
@@ -289,6 +304,21 @@ describe("DatePicker", () => {
         ]);
       });
 
+      it("can add time to a between date filter", async () => {
+        const filter = createDateFilter("between", "2020-04-01", "2020-05-01");
+        const onChange = jest.fn();
+        render(<DatePickerStateWrapper filter={filter} onChange={onChange} />);
+
+        await userEvent.click(screen.getByText("Add a time"));
+
+        expect(onChange.mock.lastCall[0]).toStrictEqual([
+          "between",
+          CREATED_AT_FIELD,
+          "2020-04-01T12:30:00",
+          "2020-05-01T12:30:00",
+        ]);
+      });
+
       it("can navigate between months on the calendar using arrows", async () => {
         render(<DatePickerStateWrapper filter={filter} />);
         await userEvent.click(screen.getByText(/specific/i));

frontend/src/metabase/admin/datamodel/components/filters/pickers/DatePicker/DatePickerFooter.tsx

@@ -62,7 +62,7 @@ const DatePickerFooter: React.FC<React.PropsWithChildren<Props>> = ({
         operator,
         field,
         start,
-        operator === "between" && !end ? start : end,
+        ...(operator === "between" ? [end ?? start] : []),
       ]);
     }
   };