问题:

I have a field with a date/time value like this:

2009-11-17 18:40:05

It's in UTC. In the query how can I convert this to EST?

I'm trying something like this but it throws an error.

// datetime is the field name
SELECT 
   FROM_TZ(TIMESTAMP TO_DATE(datetime, 'yyyy-mm-dd hh24miss'), 'EST') AS DT
FROM
   db_name

回答1:

I had to tweak it slightly to get it to work on my database, but this worked:

select from_tz(to_timestamp('2009-11-17 18:40:05','yyyy-mm-dd hh24:mi:ss'), 'UTC') 
at time zone 'America/New_York' from dual

The key is the "at time zone" syntax.

回答2:

If you want to convert a date field from UTC to EST, this worked for me:

CAST(FROM_TZ(CAST(DATE_FIELD AS TIMESTAMP), 'UTC') 
at time zone 'America/New_York' AS Date) as DESIRED_FIELD_NAME

First, I cast the desired date field (as DATE_FIELD) to a timestamp. The result of the cast is the first parameter of the FROM_TZ function, which requires the parameter to be of type TIMESTAMP. The second parameter is 'UTC', since that is what we are changing from.

Then, I cast the results of that function call back to type DATE and give it an alias.

回答3:

select to_char(systimestamp at time zone 'EST','HH') EST_TIME,
    TO_CHAR(SYSDATE,'HH') EDT_TIME,
    NEW_TIME(SYSDATE,
        (
            CASE 
                WHEN to_char(systimestamp at time zone 'EST','HH') = TO_CHAR(SYSDATE,'HH') 
                THEN 'EST'
                ELSE 'EDT'
            END
        ),'GMT') 
    from dual