public static long parseDate(byte[] data, int offset, int len) {
        int[] slice = _parseDate(data, offset, len);
        int year = slice[0];
        int month = slice[1];
        int day = slice[2];
        long epochDay = toEpochDay(year, month, day);
        return epochDay * SECONDS_PER_DAY * 1000;
    }
"2016-12-03", with "00:00:00".

@return epoch seconds, -1 if failed.
indexr-common/src/main/java/io/indexr/util/DateTimeUtil.java