java localdatetime get milliseconds
#Date and time as String to Long (millis):
String dateTimeString = "2021-09-12T16:55:18.000Z";
DateTimeFormatter formatter = DateTimeFormatter
                .ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.ENGLISH);
LocalDateTime localDateTime = LocalDateTime
        .parse(dateTimeString, formatter);
Long dateTimeMillis = localDateTime
        .atZone(ZoneId.systemDefault())
        .toInstant()
        .toEpochMilli();
