public static boolean isDayBucket(long timeBucket) {
        return timeBucket < 99999999L && timeBucket > 10000000L;
    }
The format of timeBucket in day Unit is "yyyyMMdd", so which means the TimeBucket must be between 10000000 and
99999999.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/TimeBucket.java