Date/Time Conversion

I hope that this is some silly beginner's mistake.  I have spent quite a 
bit of time
reading the PostgreSQL documentation and cannot find my error.  I have also
scanned the PostgreSQL archive and the web for help, but I have not 
found anything
to get me over the hump (it is probably out there, I just cannot find it).

All I am trying to do is convert GMT dates and times to an arbitrary
time zone.  Here is my small test database:

beta_jgw=# \d scenario1.time_test;    Table "scenario1.time_test"      Column       |         Type         | Modifiers
--------------------+----------------------+-----------gmt_hour           | integer              |gmt_date           |
date                |local_year         | integer              |local_month        | integer              |local_day
     | integer              |local_hour         | integer              |local_date         | date                 |
 

beta_jgw=# select * from scenario1.time_test;
gmt_hour |  gmt_date  | local_year | local_month | local_day | 
local_hour | local_date
----------+------------+------------+-------------+-----------+------------+------------       1 | 2002-07-06 |
  |             |           
 
|            |                14 | 2002-07-06 |            |             |           
|            |                20 | 2002-07-06 |            |             |           
|            |                18 | 2002-07-06 |            |             |           
|            |                 3 | 2002-07-06 |            |             |           
|            |                 5 | 2002-07-06 |            |             |           
|            |                10 | 2002-07-06 |            |             |           
|            |                13 | 2002-07-06 |            |             |           
|            |                 0 | 2002-07-06 |            |             |           
|            |                 2 | 2002-07-06 |            |             |           
|            |                 4 | 2002-07-06 |            |             |           
|            |                20 | 2002-07-06 |            |             |           
|            |                22 | 2002-07-06 |            |             |           
|            |                23 | 2002-07-06 |            |             |           
|            |                 7 | 2002-07-06 |            |             |           
|            |                 8 | 2002-07-06 |            |             |           
|            |                10 | 2002-07-06 |            |             |           
|            |          
Here are some simple SQL statements that I used to populate the empty 
attributes:

beta_jgw=# set time zone GMT;

beta_jgw=# update scenario1.time_test set local_hour = extract(hour from 
to_timestamp(to_char(gmt_date,'YYYY-MM-DD')||' 
'||to_char(gmt_hour,'99')||':00:00-00','YYYY-MM-DD HH24:MI:SS') at time 
zone 'EST');

beta_jgw=# update scenario1.time_test set local_year = extract(year from 
to_timestamp(to_char(gmt_date,'YYYY-MM-DD')||' 
'||to_char(gmt_hour,'99')||':00:00-00','YYYY-MM-DD HH24:MI:SS') at time 
zone 'EST');

beta_jgw=# update scenario1.time_test set local_month = extract(month 
from to_timestamp(to_char(gmt_date,'YYYY-MM-DD')||' 
'||to_char(gmt_hour,'99')||':00:00-00','YYYY-MM-DD HH24:MI:SS') at time 
zone 'EST');

beta_jgw=# update scenario1.time_test set local_day = extract(day from 
to_timestamp(to_char(gmt_date,'YYYY-MM-DD')||' 
'||to_char(gmt_hour,'99')||':00:00-00','YYYY-MM-DD HH24:MI:SS') at time 
zone 'EST');

beta_jgw=# update scenario1.time_test set local_date = 
to_date(to_char(local_year,'9999')||'-'||to_char(local_month,'99')||'-'||to_char(local_day,'99'),'YYYY-MM-DD');

And here are the contents of the table after running the SQL commands:

beta_jgw=# select * from scenario1.time_test;
gmt_hour |  gmt_date  | local_year | local_month | local_day | 
local_hour | local_date 
----------+------------+------------+-------------+-----------+------------+------------       1 | 2002-07-06 |
2002|           7 |         5 |         
 
20 | 2169-08-30      14 | 2002-07-06 |       2002 |           7 |         6 |          
9 | 2169-08-30      20 | 2002-07-06 |       2002 |           7 |         6 |         
15 | 2169-08-30      18 | 2002-07-06 |       2002 |           7 |         6 |         
13 | 2169-08-30       3 | 2002-07-06 |       2002 |           7 |         5 |         
22 | 2169-08-30       5 | 2002-07-06 |       2002 |           7 |         6 |          
0 | 2169-08-30      10 | 2002-07-06 |       2002 |           7 |         6 |          
5 | 2169-08-30      13 | 2002-07-06 |       2002 |           7 |         6 |          
8 | 2169-08-30       0 | 2002-07-06 |       2002 |           7 |         5 |         
19 | 2169-08-30       2 | 2002-07-06 |       2002 |           7 |         5 |         
21 | 2169-08-30       4 | 2002-07-06 |       2002 |           7 |         5 |         
23 | 2169-08-30      20 | 2002-07-06 |       2002 |           7 |         6 |         
15 | 2169-08-30      22 | 2002-07-06 |       2002 |           7 |         6 |         
17 | 2169-08-30      23 | 2002-07-06 |       2002 |           7 |         6 |         
18 | 2169-08-30       7 | 2002-07-06 |       2002 |           7 |         6 |          
2 | 2169-08-30       8 | 2002-07-06 |       2002 |           7 |         6 |          
3 | 2169-08-30      10 | 2002-07-06 |       2002 |           7 |         6 |          
5 | 2169-08-30

Can someone please tell me what I have done incorrectly to generate 
"local_date"?  
Again, all I want to do is convert the "gmt_hour" and "gmt_date" to an 
arbitrarily
defined time zone (in this example, I used EST).

Any help will be appreciated.

Regards,

Jim