$dateFormatter
$dateFormatter : ?\Drupal\Core\Datetime\DateFormatterInterface
The date formatter.
Renders unix microseconds as a date, keeping the part below the second.
Strata stores times in microseconds because a site can write the same subject twice in one second and the order matters. Rendering that through the ordinary date field would divide it by a million and lose the part that made it unambiguous, so a timeline of a busy second would show the same instant repeated.
The fractional part is shown by default for exactly that reason, and can be switched off for a report where the second is enough.