I'm using hibernate 3.2.1.ga and got stuck with the problem:
value of the field of type Timestamp changes during update.
The mapping is

<class name="misprint.model.DomainExpired" proxy="misprint.model.DomainExpired" table="mpDomainExpired">
<cache usage="nonstrict-read-write"/>
<id column="domainExpiredId" name="id" type="java.lang.String" unsaved-value="null">
<generator class="uuid.hex"/>
</id>
<property column="domainExpiredAccessDate" not-null="false" name="accessDate" type="java.sql.Timestamp" unique="false"/>
<property column="domainExpiredExpireDate" not-null="false" name="expiredDate" type="java.sql.Timestamp" unique="false"/>
...
</class>

The DomainExpired class:

public class DomainExpired extends DomainMissprint {
private String id;
private Timestamp expiredDate;
private Timestamp accessDate;
....
}
And I have a function

public void updateDomain(Domain d) throws SNException {
d.setAccessDate(new Timestamp(new Date().getTime()));
hu.updateObject(d);
}
hu.updateObject code:
public void updateObject(Model obj) throws SNException {
try {
Session sess = DBResource.getInstance().getSessionFactory().openSession();
Transaction tx = sess.beginTransaction();
try {
sess.update(obj);
tx.commit();
} catch (Exception e) {
tx.rollback();
throw new SNException(e);
} finally {
sess.close();
}
} catch (Exception e) {
throw new SNException(e);
}
}

When I run updateDomain, the value of d.expiredDate is being
changed (It is decreased by 1 day).
Before call of updateDomain() d.expiredDate == '20.06.2007', after
call it becomes '19.06.2007'.
Problem doesn't occurs each time. Any ideas?

Yep! I've sort this problem out by myself.
The reason was the Time zone of virtal mashine. It deffers from the time zone of the database. The solution was to set the timezone:
TimeZone.setDefault(TimeZone.getTimeZone("GMT-7"));