Casting Local Time to UTC Formating Incorrect - sql

Question

HIRE_DATE is in a 'DATE' column. The timestamp is local (Los Angeles); I would like to convert it to UTC.
I can't for the life of me fathom why the UTC output is mangled (Last 2 digits of YY is the DD; and vice-versa) -- and the time does not convert to UTC.
HIRE_DATE: 30/04/2019 12:00:00 AM
select from_tz(to_timestamp(HIRE_DATE,'DD-MM-YY HH24:MI:SS'), 'America/Los_Angeles') at time zone 'UTC' from TABLE
OUTPUT: 19/04/2030 12:00:00 AM

Answer 1

If HIRE_DATE is a DATE data type then you don't need TO_TIMESTAMP.
TO_TIMESTAMP is used to convert a string (i.e. VARCHAR2) into a TIMESTAMP value but you have a DATE value.
Just do
select from_tz(CAST(HIRE_DATE AS TIMESTAMP), 'America/Los_Angeles') at time zone 'UTC'
from TABLE
Actually I don't understand why FROM_TZ does not accept DATE values whereas almost any other date/timestamp related function accept either DATE or TIMESTAMP value as input.
Note, the default output display format of this query is defined by current user session NLS_TIMESTAMP_TZ_FORMAT setting. If you are not satisfied with the output format, either change NLS_TIMESTAMP_TZ_FORMAT setting by executing ALTER SESSION SET NLS_TIMESTAMP_TZ_FORMAT = '...' or use TO_CHAR function to set output format explicitly.
Instead of
... AT TIME ZONE 'UTC'
you can also use
SYS_EXTRACT_UTC(...)
The upper returns a TIMESTAMP WITH TIME ZONE value, the second one returns a TIMESTAMP value.

Answer 2

Would this do any good?
SQL> select from_tz(cast (sysdate as timestamp), 'UTC') result from dual;
RESULT
---------------------------------------------------------------------------
27.09.20 10:59:28,000000 UTC
Or, in your case
select from_tz(cast (hire_date as timestamp), 'UTC' from dual
No need to apply any format mask to hire_date as it is a DATE datatype (at least, that's what you said).

Answer 3

You use the word "convert" which can mean one of two things:
change the data type, which is what FROM_TZ does
change the value from one time zone to another, which FROM_TZ does not do.
You didn't give your expected output, so we may misunderstand.
To change the data type:
with data(dte) as (
select date '2019-04-30' + interval '12' hour from dual
)
select from_tz(cast(dte as timestamp), 'America/Los_Angeles') from data
FROM_TZ(CAST(DTEASTIMESTAMP),'AMERICA/LOS_ANGELES')
30-APR-19 12.00.00.000000 PM AMERICA/LOS_ANGELES
To get the simultaneous datetime value in UTC:
with data(dte) as (
select date '2019-04-30' + interval '12' hour from dual
)
select cast(sys_extract_utc(from_tz(cast(dte as timestamp), 'America/Los_Angeles')) as date) from data
CAST(SYS_EXTRACT_UTC(FROM_TZ(CAST(DTEASTIMESTAMP),'AMERICA/LOS_ANGELES'))ASDATE)
2019-04-30 19:00:00