private void copyDateTime(
      String key,
      CalendarEventModel.CalendarEventTime dateTime,
      Map<String, Object> graphCalendar) {
    Map<String, String> graphDateTime = new HashMap<>();
    graphDateTime.put(
        "dateTime",
        dateTime.getDateTime().atZoneSameInstant(ZoneId.of("UTC")).toLocalDateTime().toString());
    graphDateTime.put("timeZone", "UTC");
    graphCalendar.put(key, graphDateTime);
  }
Maps from a transfer event type to a Graph API event resource as defined by:
https://developer.microsoft.com/en-us/graph/docs/api-reference/v1.0/resources/event.
extensions/data-transfer/portability-data-transfer-microsoft/src/main/java/org/datatransferproject/transfer/microsoft/transformer/calendar/ToGraphEventTransformer.java