Tracing: Show start time of trace with milliseconds precision (#42132) (#42138)

* Tracing header: Add setting to show start time with ms

* Add test

* Update test

(cherry picked from commit aefb2659ec)

Co-authored-by: Ivana Huckova <30407135+ivanahuckova@users.noreply.github.com>

packages/jaeger-ui-components/src/TracePageHeader/TracePageHeader.test.js

@@ -60,6 +60,11 @@ describe('<TracePageHeader>', () => {
     });
   });
 
+  it('renders start time in header with millisecond precision', () => {
+    const startTimeMs = wrapper.find(LabeledList).props().items[0].value.props.children[1].props.children;
+    expect(startTimeMs).toMatch(/:\d\d\.\d\d\d/g);
+  });
+
   it('renders a <SpanGraph>', () => {
     expect(wrapper.find(SpanGraph).length).toBe(1);
   });

packages/jaeger-ui-components/src/TracePageHeader/TracePageHeader.tsx

@@ -167,7 +167,7 @@ export const HEADER_ITEMS = [
     label: 'Trace Start',
     renderer(trace: Trace, timeZone: TimeZone, styles: ReturnType<typeof getStyles>) {
       // Convert date from micro to milli seconds
-      const dateStr = dateTimeFormat(trace.startTime / 1000, { timeZone });
+      const dateStr = dateTimeFormat(trace.startTime / 1000, { timeZone, defaultWithMS: true });
       const match = dateStr.match(/^(.+)(:\d\d\.\d+)$/);
       return match ? (
         <span className={styles.TracePageHeaderOverviewItemValue}>