Getting DBs Timezone In Oracle 11.2.0.3?

I need the timezone of the server that the DB sits on. I don't want the offset. I need the region name. This is because some regions use daylight savings time and some do not. Plus an SA can change the time of the OS. Another company manages our servers and DBs in production and we don't have contact with them. We could use a lookup talbe and just populate it, then update it when we find out what it is in production. The problem is that I have seen cases where the timezone on servers change. Considering the lack of contact between the teams, we really need a reliable way to get the timezone out of the DB.

We tried several ways. My list is below and I explain why this is not working.

examples:

sessiontimezone: this is the timezone of my server. In theory it should be the same as the DB. We cannot take the risk that this will be out of sync. dbtimezone: This gives the offset. Such as -5:00 for US EST. There are multiple regions that have this. Some do not use daylight savings time and some do. We would need America/New York instead.

sessiontimezone gives the timezone setting for the client. This can be altered.
dbtimezone just gives the offset such as -5:00

We get data feeds from different parts of the world. We get some data based data that is local to that regions timezone. We need to partition on this field. So we need to add a field to the DB and normalize it to the time local to our DB Server. So if we get a record from california and the DB is on a server in US EAST, we add 3 hours. The offset won't work...

1. a timezone that we are getting from may not be in daylight savings time. We are partitioning by hour.

2. We would hit daylight savings time in New York before we hit it in California, so we would need to account for that in the math.

This hourly partition is a fixed and hard requirement. We need this to be absolutely accurate.

Here is what we tried:

What I want (pseudo-code): “Select XXX as timezone_region_name” to return “America/New_York” or “UTC”. It may be that the timezone was not set for the database at install time, and if it were, these queuries would work.

-- FAILED
SELECT DBTIMEZONE FROM dual;

--FAILED
select systimestamp, to_char(systimestamp, 'TZR'), extract (timezone_region from systimestamp) from dual;

--FAILED
SELECT systimestamp
     AT TIME ZONE DBTIMEZONE "DB Time"
FROM DUAL;

--FAILED
select to_char(systimestamp, 'TZR') from dual;