How to get Date Difference in hour using HQL

I've to get difference between current date and the date stored in database in hours. In PostgreSQL, I'm able to do it using the following query:

SELECT storage_time, extract(epoch from (localtimestamp - storage_time))/3600 as diff_hour FROM some_table;

This gives me the difference between dates in hour:

      storage_time       |     diff_hour      -------------------------+------------------- 2014-02-03 19:37:39.481 |  44.4788805811111 2014-02-03 19:40:28.201 |  44.4320139144444 2014-01-29 18:25:12.828 |  165.686284192222 2014-02-03 19:25:56.861 |  44.6740528033333 2014-02-05 15:53:38.178 | 0.212575858888889 2014-01-30 15:53:38.61  |  144.212455858889

Now, I'm facing difficulty porting it to Hibernate Query Language. I've tried many variations, but I'm unable to get epoch from date difference. This certainly doesn't work:

"FROM SomeEntity "+"WHERE someAttribute = :attr "+"AND epoch(localtimestamp - deviceInfo.storageTime) / 3600 > :threshold_hour";

When I run this command, I get following exception:

org.hibernate.exception.SQLGrammarException: could not extract ResultSet    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2102)    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1835)    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:500)    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:388)    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:273)    at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:93)    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:56)    at org.hibernate.loader.Loader.getResultSet(Loader.java:2040)    at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1837)    at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1816)    at org.hibernate.loader.Loader.doQuery(Loader.java:900)    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:342)    at org.hibernate.loader.Loader.doList(Loader.java:2526)    at org.hibernate.loader.Loader.doList(Loader.java:2512)    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2342)    at org.hibernate.loader.Loader.list(Loader.java:2337)    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:495)    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:357)    at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:195)    at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1275)    at org.hibernate.internal.QueryImpl.list(QueryImpl.java:101)

I ran the query like this:

Query query = sessionFactory.getCurrentSession()                    .getNamedQuery(GET_NON_EXPIRED_ENTITY)                    .setString("attr", attr)                    .setInteger("threshold_hour", thresholdHour);List<SomeEntity> instances = query.list();

Exception is coming at 2nd line, when I call list().

But, when I change epoch() function to day(), in hibernate query, it runs without exception, but of course with unexpected result.

Is there any way I can get the same behavior of PostgreSQL query in HQL?