How to Subtract number of days from current date in HQL query

You can use date_Sub in a native SQL query (not a HQL query!):

 "from Users where createdDate =   DATE( DATE_SUB( NOW() , INTERVAL 21 DAY ) )" 

The solution with HQL is quite simple:

        final long time = System.currentTimeMillis() - java.time.Duration.ofDays(21).toMillis();
        final javax.persistence.Query query = entityManagerOrSession.createQuery(
                "SELECT x FROM users x WHERE x.createddate> :time");
        query.setParameter("time", new java.sql.Timestamp(time));