private static int[] _parseDate(byte[] data, int offset, int len) {
        int[] slice = splitInts(3, 3, '-', data, offset, len);
        if (slice == null) {
            throw new IllegalArgumentException("Illegal DATE format: " + UTF8Util.fromUtf8(data, offset, len));
        }
        return slice;
    }
"2016-12-03", with "00:00:00".

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