code: protected function getTime($timestamp)
      {
          $parts = explode('.', sprintf('%F', $timestamp));
  
          return date('Y-m-d H:i:s', $parts[0]) . ($this->microtime ? ('.' . $parts[1]) : '');
      }
docs: Returns formatted ('Y-m-d H:i:s') timestamp for message.
  If [[microtime]] is configured to true it will return format 'Y-m-d H:i:s.u'.
  @param float $timestamp
  @return string
  @since 2.0.13