TImezone calculations

Question

I am using an Oracle 8.1.7 DB and trying to calculate the systems timezone within a PL/SQL function. Does anyone have any suggestions or sample code???
Thanks in advance

Answer 1

Here are 2 documents from Metalink:
1.
PURPOSE
The aim of this article is to give customers some possibilities when working in a world wide context.
SCOPE & APPLICATION
Replication , Sqlplus, SQL
TIMEZONES IN SQL*Plus
The common method to synchronize time when working in a worldwide context is to set the timezone within the Operating System, (OS). The Oracle database will inherit the timezone of the OS environment.But what will happen if the instance is located in Paris(GMT+1) and you want to submit a DML throught a dblink located in Tokyo (GMT+9)?
This can be achieved by using the SQL built-in function NEW_TIME.
NEW_TIME consists of 3 entries:
- the first one corresponds to a DATE/TIME in the local timezone
- the second one is the correponding timezone (eg. GMT, EST, etc.)
- the last one is the timezone in which the date will be converted
Below are the valid timezones used by NEW_TIME:
AST,ADT Atlantic Standard/Daylight Time (GMT-4/GMT-3)
BST,BDT Bering Standard/Daylight Time (GMT-11/GMT-10)
CST,CDT Central Standard/Daylight Time (GMT-6/GMT-5)
EST,EDT Eastern Standard/Daylight Time (GMT-5/GMT-4)
GMT Greenwich Mean Time
HST,HDT Alaska-Hawaii Standard/Daylight Time (GMT-10/GMT-9)
MST,MDT Mountain Standard/Daylight Time (GMT-7/GMT-6)
NST Newfoundland Standard Time (GMT-3.5)
PST,PDT Pacific Standard/Daylight Time (GMT-8/GMT-7)
YST,YDT Yukon Standard/Daylight Time (GMT-9/GMT-8)
As you will note, this list does not include all the timezones for the world.To use the NEW_TIME function with timezones, other than those listed, you will need to manipulate the current time via a sysdate function.
Example 1
Site A:Paris Site B Tokyo
dblnk1 pointing at siteB dblnk2 pointing at siteA
Site A is GMT+1 and Site B is GMT-9.
From SiteB with TZ(OS timezone set to GMT-9)
Suppose that it's 9:00 PM in Tokyo:
SQL> select sysdate from dual@dblnk2
Results in 9:00 PM
SQL> select NEW_TIME(sysdate+1/24,'HDT','GMT') from dual@dblnk2
Results in 1:00 PM which corresponds to the time in Paris.
This function is useful when INSERTING,UPDATING OR DELETING.
2.
Problem Description:
====================
In SQL, how do you add or subtract time increments, other than days, to a date?
Search Words: second, seconds, minute, minutes, hour, day
Problem Explanation:
====================
Example
How do you subtract 2 hours from SYSDATE?
Solution Description:
=====================
An Oracle date is in units of a day, so express the desired time interval as a fraction of a day.
o To add n day(s), add n to the date.
Example
SELECT TO_CHAR(hiredate+(n), 'DD-MON-YY HH:MI:SS') plusday
FROM emp;
o To add n hour(s), add n/24 to the date.
n hr x 1 day
24 hrs
Example
SELECT TO_CHAR(hiredate+(n/24), 'DD-MON-YY HH:MI:SS') plushour
FROM emp;
o To add n minute(s), add n/24/60 to the date:
n min x 1 hr x 1 day
60 min 24 hrs
Example
SELECT TO_CHAR(hiredate+(n/24/60), 'DD-MON-YY HH:MI:SS') plusmin
FROM emp;
o To add n second(s), add n/24/60/60 to the date.
n sec x 1 min x 1 hr x 1 day
60 sec 60 min 24 hrs
Example
SELECT TO_CHAR(hiredate+(n/24/60/60), 'DD-MON-YY HH:MI:SS') plussec
FROM emp;
Solution Explanation:
=====================
Example
To subtract 2 hours from SYSDATE:
1. Express 2 hours as a fraction of a day:
2 hrs x 1 day = 2 = 1 day
24 hrs 24 12
2. Use the following syntax:
SELECT SYSDATE - 1/12
FROM dual;
This returns the time 2 hours ago.
Maybe it will be a little help for you.