java - 文字列を ZonedDateTime に変換できません: DateTimeParseException

Question

文字列を JSON から ZonedDateTime に変換しようとしています

static String getWatchTime(JSONObject aJson, JSONObject bJson) {
    long difference = 0 ;
    try {
        String aTime = aJson.getString("time_utc_8");
        String bTime = bJson.getString("time_utc_8");

        String pattern = "yyyy-MM-dd HH:mm:ss.SSSSSS";
        DateTimeFormatter Parser = DateTimeFormatter.ofPattern(pattern).ISO_DATE;

        System.out.println(aTime);

        ZonedDateTime a = ZonedDateTime.parse(aTime, Parser);
        ZonedDateTime b = ZonedDateTime.parse(bTime, Parser);

        ChronoUnit unit = null;
        difference = unit.between(a, b);

        System.out.println(difference);

    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    String t = difference +"";
    return t;

}

そして常にエラーが発生します

Exception in thread "main" java.time.format.DateTimeParseException: Text '2016-06-28 22:29:44.700228' could not be parsed: Unable to obtain OffsetDateTime from TemporalAccessor: {},ISO resolved to 2016-06-28T22:29:44.700228 of type java.time.format.Parsed
at java.time.format.DateTimeFormatter.createError(Unknown Source)
at java.time.format.DateTimeFormatter.parse(Unknown Source)
at java.time.OffsetDateTime.parse(Unknown Source)
at Q2.getWatchTime(Q2.java:321)
at Q2.WatchTime(Q2.java:265)
at Q2.main(Q2.java:31)

これら2つの日付の違いを取得したい。試してみましSimpleDateFormatたが、ミルのエラー結果が得られます。