lib/utils/tracking.js/resolveTimestamp
function resolveTimestamp(event) {
  try {
    if (event.data) return event.data.timestamp * 1000 || null;
    if (event.properties) return event.properties.general.timestamp || null;
    return null;
  } catch (error) {
    let eventString;
    try {
      eventString = JSON.stringify(event, null, 2);
    } catch (stringifyError) {
      // ignore;
    }
    logError(`Could not resolve timestamp, out of event: ${eventString}`, error);
    return null;
  }
}