public static boolean isHourBucket(long timeBucket) {
        return timeBucket < 9999999999L && timeBucket > 1000000000L;
    }
The format of timeBucket in hour Unit is "yyyyMMddHH", so which means the TimeBucket must be between 1000000000
and 9999999999.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/TimeBucket.java