First of all, you should make clear whether you want the current date of your database engine or the one of your application server...
If the value of your LST_MOD_DATE field is set by your application at the time Hibernate persist the entity, then you had better to build your query using the current time obtained from your application as well.
Example:
Code:
// compute max mod date
Calendar cal = Calendar.getInstance();
cal.add(Calendar.DAY_OF_YEAR, -15);
Date maxModDate = cal.getTime();
// query database
Query query = session.createQuery("from data where lst_mod_date <= :maxModDate");
query.setParameter("maxModDate", maxModDate");
List result = query.list();
On the other hand, if your LST_MOD_DATE field is set by the database (using trigger or whatever) then it is initialized with the database's time. In this case, you should make use of database date functions in your criteria.
The syntax may be database specific. For this you probably have to check the dialect that applies to your database and/or tell hibernate what functions are available (configuration issue).
Hope this helps...