Timezone conversion in PLSQL - sql

Question

I need to convert the sysdate and time to a particular timezone like EST. I can't assume my current time zone.
How to convert this in plsql? Please help me.

Answer 1

Assuming you have a TIMESTAMP WITH TIME ZONE (such as systimestamp), you can use the AT TIME ZONE syntax. For example, I can take the current systimestamp and convert it to UTC (GMT), Eastern, and Pacific time zones by specifying different time zone names.
SQL> ed
Wrote file afiedt.buf
1 select systimestamp at time zone 'UTC' current_time_in_utc,
2 systimestamp at time zone 'Us/Eastern' current_time_in_est,
3 systimestamp at time zone 'US/Pacific' current_time_in_pst
4* from dual
SQL> /
CURRENT_TIME_IN_UTC
---------------------------------------------------------------------------
CURRENT_TIME_IN_EST
---------------------------------------------------------------------------
CURRENT_TIME_IN_PST
---------------------------------------------------------------------------
26-APR-12 05.36.11.802000 PM UTC
26-APR-12 01.36.11.802000 PM US/EASTERN
26-APR-12 10.36.11.802000 AM US/PACIFIC

Answer 2

Oracle already has a timezone table:
SELECT tzname, tzabbrev from V$TIMEZONE_NAMES
SELECT TZ_OFFSET('US/Eastern') FROM DUAL;
Get the current time in EPT for use in a SQL statement:
select to_timestamp(to_char(TRUNC(LOCALTIMESTAMP - 5/1440, 'MI'),'mm/dd/yyyy hh24:mi'),'mm/dd/yyyy hh24:mi') FROM DUAL;
Oracle's 11g SQL reference is pretty good and available online here: http://docs.oracle.com/cd/B28359_01/server.111/b28286/toc.htm
You can quickly look up the following functions, which I'm sure you'll find helpful:
current_timestamp
dbtimezone
localtimestamp
trun(date)
sessiontimezone
sys_extract_utc
systimestamp
to_timestamp
to_timestamp_tz
tz_offset
ALTER SESSION SET TIME_ZONE = '+00:00'; -- you will now see times in UTC instead of EPT
Current date & time in varying timezones
Return current date & time (sysdate) in local prevailing time
Select sysdate from dual;
select LOCALTIMESTAMP FROM DUAL;
Return current date as UTC
select LOCALTIMESTAMP at time zone '+00:00' FROM DUAL
-- Instead of using sysdate and to_date, try using localtimestamp, to_timestamp and to_timestamp_tz. They are like sysdate and to_date but add on timezone functionality.
select LOCALTIMESTAMP at time zone '+00:00' FROM DUAL; –- returns essentially the same as sysdate but in UTC
or
ALTER SESSION SET TIME_ZONE = 'UTC';
select LOCALTIMESTAMP FROM DUAL –- after setting session time_zone to ‘UTC’ this will now return a UTC timestamp
Time zone conversion
Get the current time in UTC for use in a SQL statement.
-- Get current time in UTC format and subtract 5 minutes.
LOCALTIMESTAMP at time zone '+00:00' - 5/1440
-- Trunc the time to eliminate seconds
TRUNC(LOCALTIMESTAMP at time zone '+00:00' - 5/1440, 'MI')
-- Convert to characters then back to datetime.
to_timestamp(to_char(TRUNC(LOCALTIMESTAMP at time zone '+00:00' - 5/1440, 'MI'),'mm/dd/yyyy hh24:mi'),'mm/dd/yyyy hh24:mi')
-- Select from dual to show it works.
select to_timestamp(to_char(TRUNC(LOCALTIMESTAMP at time zone '+00:00' - 5/1440, 'MI'),'mm/dd/yyyy hh24:mi'),'mm/dd/yyyy hh24:mi') FROM DUAL;
Get the current time in EPT for use in a SQL statement.
-- Get current time in UTC format and subtract 5 minutes.
ALTER SESSION SET TIME_ZONE = 'US/Eastern'; -- set to EPT time
select LOCALTIMESTAMP from dual - 5/1440
-- Trunc the time to eliminate seconds
TRUNC(LOCALTIMESTAMP - 5/1440, 'MI')
-- Convert to characters then back to datetime.
to_timestamp(to_char(TRUNC(LOCALTIMESTAMP - 5/1440, 'MI'),'mm/dd/yyyy hh24:mi'),'mm/dd/yyyy hh24:mi')
-- Select from dual to show it works.
select to_timestamp(to_char(TRUNC(LOCALTIMESTAMP - 5/1440, 'MI'),'mm/dd/yyyy hh24:mi'),'mm/dd/yyyy hh24:mi') FROM DUAL;
Return DB and Session time zone functions
ALTER SESSION SET TIME_ZONE = '+00:00'; -- you will now see times in UTC instead of EPT
ALTER SESSION SET NLS_DATE_FORMAT = 'MM/DD/YYYY HH24:MI:SS';
ALTER SESSION SET TIME_ZONE = '+00:00'; -- you will now see times in UTC instead of EPT
ALTER SESSION SET TIME_ZONE = 'UTC'; -- set to UTC time same as command above
SELECT DBTIMEZONE , SESSIONTIMEZONE, CURRENT_TIMESTAMP, LOCALTIMESTAMP, systimestamp, sysdate FROM DUAL; -- see the results
ALTER SESSION SET TIME_ZONE = 'US/Eastern'; -- set to EPT time
SELECT DBTIMEZONE , SESSIONTIMEZONE, CURRENT_TIMESTAMP, LOCALTIMESTAMP, systimestamp, sysdate FROM DUAL; -- see the results
SELECT TO_TIMESTAMP_TZ('05/16/2014 11:26:48 -04:00',
'MM/DD/YYYY HH:MI:SS TZH:TZM') FROM DUAL;
SELECT tzname, tzabbrev from V$TIMEZONE_NAMES where tzabbrev = 'EPT';
SELECT TZ_OFFSET('US/Eastern') FROM DUAL;
-- The following example casts a null column in a UNION operation as TIMESTAMP WITH LOCAL TIME ZONE using the sample tables oe.order_items and oe.orders:
SELECT order_id, line_item_id,
CAST(NULL AS TIMESTAMP WITH LOCAL TIME ZONE) order_date
FROM order_items
UNION
SELECT order_id, to_number(null), order_date
FROM orders;
Date Time and Timezone (TO_TIMESTAMP_TZ)
TO_TIMESTAMP_TZ converts char of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to a value of TIMESTAMP WITH TIME ZONEdatatype.
Examples:
The following example converts a character string to a value of TIMESTAMP WITH TIME ZONE:
SELECT TO_TIMESTAMP_TZ('1999-12-01 11:00:00 -8:00',
'YYYY-MM-DD HH:MI:SS TZH:TZM') FROM DUAL;
TO_TIMESTAMP_TZ('1999-12-0111:00:00-08:00','YYYY-MM-DDHH:MI:SSTZH:TZM')
The following example casts a null column in a UNION operation as TIMESTAMP WITH LOCAL TIME ZONE using the sample tablesoe.order_items and oe.orders:
SELECT order_id, line_item_id,
CAST(NULL AS TIMESTAMP WITH LOCAL TIME ZONE) order_date
FROM order_items
UNION
SELECT order_id, to_number(null), order_date
FROM orders;
Set Date & time formats
ALTER SESSION SET NLS_DATE_FORMAT = 'MM/DD/YYYY HH24:MI:SS';
SELECT CURRENT_TIMESTAMP, LOCALTIMESTAMP FROM DUAL;
Set current/local Timezone
ALTER SESSION SET TIME_ZONE = '-5:00';
ALTER SESSION SET NLS_DATE_FORMAT = 'MM/DD/YYYY HH24:MI:SS';
SELECT CURRENT_TIMESTAMP, LOCALTIMESTAMP FROM DUAL;
Local Time (LOCALTIMESTAMP)
LOCALTIMESTAMP returns the current date and time in the session time zone in a value of datatype TIMESTAMP. The difference between this function and CURRENT_TIMESTAMP is that LOCALTIMESTAMP returns a TIMESTAMP value while CURRENT_TIMESTAMPreturns a TIMESTAMP WITH TIME ZONE value.
ALTER SESSION SET TIME_ZONE = '-5:00';
ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';
SELECT CURRENT_TIMESTAMP, LOCALTIMESTAMP FROM DUAL;
The following statement uses the correct format mask to match the return type of LOCALTIMESTAMP:
INSERT INTO local_test VALUES
(TO_TIMESTAMP(LOCALTIMESTAMP, 'DD-MON-RR HH.MI.SSXFF PM'));
The code above is required to include the TIME ZONE portion of the return type of the function
Current Timestamp (CURRENT_TIMESTAMP)
CURRENT_TIMESTAMP returns the current date and time in the session time zone, in a value of datatype TIMESTAMP WITH TIMEZONE. The time zone offset reflects the current local time of the SQL session
ALTER SESSION SET TIME_ZONE = '-5:0';
ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';
SELECT SESSIONTIMEZONE, CURRENT_TIMESTAMP FROM DUAL;

Answer 3

How about this?
select to_timestamp_tz(to_char(sysdate,'YYYY-MM-DD HH24:MI:SS') || ' ' || 'FROM_TIME_ZONE', 'YYYY-MM-DD HH24:MI:SS TZR') at time zone 'TO_TIME_ZONE'
from dual;

Answer 4

Try this:
CREATE TABLE TIMEZONES (ZONE CHAR(1) PRIMARY KEY,
NAMES VARCHAR2(25) NOT NULL,
OFFSET_HOURS NUMBER NOT NULL);
Populate it as follows:
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('Z', 'GMT', 0);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('N', '-1', -1);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('O', '-2', -2);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('P', '-3', -3);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('Q', '-4 EDT', -4);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('R', 'EST CDT', -5);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('S', 'CST MDT', -6);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('T', 'MST PDT', -7);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('U', 'PST', -8);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('V', '-9', -9);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('W', '-10', -10);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('X', '-11', -11);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('Y', '-12', -12);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('A', '1', -1);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('B', '2', -2);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('C', '3', -3);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('D', '4', -4);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('E', '5', -5);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('F', '6', -6);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('G', '7', -7);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('H', '8', -8);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('I', '9', -9);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('K', '10', -10);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('L', '11', -11);
INSERT INTO TIMEZONES (ZONE, NAMES, OFFSET_HOURS) VALUES ('M', '12', -12);
Given the above you can then do
SELECT SYS_EXTRACT_UTC(SYSTIMESTAMP) + (tz.OFFSET_HOURS / 24)
FROM TIMEZONES tz
WHERE tz.NAMES LIKE '%EDT%';
or
WHERE tz.ZONE = 'Q'
to get the local time in the -4 timezone.
Share and enjoy.

Answer 5

The following will give you the current EST time (UTC - 5 hours) without taking into account daylight savings:
SELECT SYS_EXTRACT_UTC(SYSTIMESTAMP) FROM DUAL
In order to take daylight savings into account, you have 2 options:
Write a function to calculate which dates daylight saving time changes occur on
Populate a table containing these dates
If you only need to support the EST time zone then writing a function may be the way to go; otherwise I'd recommend populating a table containing these dates as they vary between time zones.

Answer 6

All of the methods so far work nicely when working with a current timestamp. I noticed however that Oracle's tz_offset will give you the prevailing time offset. For example, in July,
SELECT TZ_OFFSET('US/Eastern') FROM DUAL;
results in '-04:00.' In January, the same statement results in '-05:00.' So, if you want to convert a date stored in the database (as opposed to the current system or session time), you have to do some development.
You might note that
SELECT TZ_OFFSET('EST') FROM DUAL;
always returns '-05:00.' Unfortunately, a quick test of the other US standard times (Central, Mountain and Pacific) showed different results. Run the following to see for yourself. I ran the following on June 16, while DST was in effect.
SELECT TZ_OFFSET('US/Eastern'), TZ_OFFSET('EST'), TZ_OFFSET('EST5EDT') FROM DUAL;
SELECT TZ_OFFSET('US/Central'), TZ_OFFSET('CST'), TZ_OFFSET('CST6CDT') FROM DUAL;
SELECT TZ_OFFSET('US/Mountain'), TZ_OFFSET('MST'), TZ_OFFSET('MST7MDT') FROM DUAL;
SELECT TZ_OFFSET('US/Pacific'), TZ_OFFSET('PST'), TZ_OFFSET('PST8PDT') FROM DUAL;
-04:00 -05:00 -04:00
-05:00 -05:00 -05:00
-06:00 -07:00 -06:00
-07:00 -07:00 -07:00
The results are somewhat frustrating. From a quick sampling, almost all tz_offset queries appear to respond with the the current prevailing time. This useful when you are working with conversions for the current time, but falls flat when working with times that are pulled from the database.
Now, I can write code to determine if I'm in standard or prevailing time. However, there is no way that I see to consistently pull a tz_offset for standard or daylight times, just prevailing.
This leaves the developer with a need to create their own table as Bob Jarvis did above to hack around the problem as I did in the code below.
ALTER SESSION SET NLS_DATE_FORMAT = 'MM/DD/YYYY HH24:MI:SS';
Declare
-- ******** User declarations begin here ******** --
-- ******** User declarations end here ******** --
/******************* All Declarations of Variables and Functions below this point support Time Zone Conversion (Convert_TZ function) *******************/
-- TimeZone Conversion Procedure
-- User Input (Parameters)
input_date date := TO_TIMESTAMP_TZ('7/1/2009 18:00','mm/dd/yyyy hh24:mi'); -- Try: LocalTimestamp; or TO_TIMESTAMP('2/1/2009 13:00','mm/dd/yyyy hh24:mi')
--input_date date := LocalTimestamp;
input_TZ varchar(3) := 'GMT'; -- Exmaples: EST, EDT or EPT for Eastern Standard, Daylight or Prevailing, respectively.
output_TZ varchar(3) := 'EPT'; --
-- Variables
type date_array is table of date;
return_date date := localtimestamp;
temp_date date := to_date('10/27/1974 02:00','mm/dd/yyyy hh24:mi');
type str_array is table of varchar2(10);
dow_list str_array;
Function dst_start_stop (input_date DATE)
RETURN date_array
AS
year_part number(4);
start_week number(1) := 0; -- week of month: -1=last, 1=1st, 2=nd, 0=fixed date (like 1974 and 1975)
stop_week number(1) := 0; -- week of month: -1=last, 1=1st, 2=nd, 0=fixed date (like 1974 and 1975)
dst_start date := to_date('01/06/1974 23:59','mm/dd/yyyy hh24:mi');
dst_stop date := to_date('10/27/1974 23:59','mm/dd/yyyy hh24:mi');
dst_date date := dst_start;
dst_msg varchar2(500) := ' ';
inc_dec number := 0;
Cnt number(1) := 0;
dst_dow number(1) := 1; -- 1=Sunday, 2=Monday, etc.
i number;
dst_range date_array;
BEGIN
dst_range := date_array();
dst_range.extend(2);
dst_range(1) := temp_date;
dst_range(2) := temp_date;
DBMS_OUTPUT.PUT_LINE(' ** Start: dst_start_stop Func **');
--insert into dst_range values(dst_start,dst_stop);
--dst_range(1) := dst_start;
--dst_range(2) := dst_stop;
year_part := to_number(to_char(input_date,'YYYY'));
DBMS_OUTPUT.PUT_LINE(' Year: '||year_part);
-- Determine DST formula based on year of input_date
If year_part > 9999 Then -- Invalid TempYear > 9999
dst_msg := 'N/A. I can''t guess if DST will be applied after 9999. Standard Time returned. ';
Goto found_start_stop;
ElsIf year_part >= 2007 Then -- 2007 forward. Latest DST Rules used after 2007.
dst_msg := '2007 forward: Third National DST Standard. ';
--dst_msg := dst_msg || 'Spring Forward 2:00 AM second Sunday in March (skip 02:00:00 through 02:59:59, I.E. skip from 01:59:59 to 03:00:00). '
--dst_msg := dst_msg || 'Fall Back 2:00 AM first Sunday in November (repeat 02:00:00 to 02:59:59, I.E. jump back from 02:59:59 to 02:00:00 once). '
DBMS_OUTPUT.PUT_LINE(' '||dst_msg);
dst_start := to_date('03/01/'||year_part||' 02:00','mm/dd/yyyy hh24:mi');
start_week := 2; -- 2nd Sunday in March
dst_stop := to_date('11/01/'||year_part||' 02:00','mm/dd/yyyy hh24:mi');
stop_week := 1; -- 1st Sunday in November
ElsIf year_part >= 1987 Then -- 1987 thru 2006.
dst_msg := '1987 thru 2006: Second National DST Standard. ';
--dst_msg := dst_msg || 'Spring Forward 2:00 AM first Sunday in April (skip 02:00:00 through 02:59:59, I.E. skip from 01:59:59 to 03:00:00). ';
--dst_msg := dst_msg || 'Fall Back 2:00 AM last Sunday in October (repeat 02:00:00 to 02:59:59, I.E. jump back from 02:59:59 to 02:00:00 once). ';
DBMS_OUTPUT.PUT_LINE(' '||dst_msg);
start_week := 1;
dst_start := to_date('04/01/'||year_part||' 02:00','mm/dd/yyyy hh24:mi');
stop_week := -1;
dst_stop := to_date('10/31/'||year_part||' 02:00','mm/dd/yyyy hh24:mi');
ElsIf year_part >= 1976 Then -- 1976 thru 1986 OLD DST Rules used 1961 thru 1973.
dst_msg := '1976 thru 1986: First National DST Standard (resumed after 1974-1975 extended DST trials). ';
--dst_msg := dst_msg || 'Spring Forward 2:00 AM last Sunday in April (skip 02:00:00 through 02:59:59, I.E. skip from 01:59:59 to 03:00:00). ';
--dst_msg := dst_msg || 'Fall Back 2:00 AM last Sunday in October (repeat 02:00:00 to 02:59:59, I.E. jump back from 02:59:59 to 02:00:00 once). ';
DBMS_OUTPUT.PUT_LINE(' '||dst_msg);
start_week := -1;
dst_start := to_date('04/30/'||year_part||' 02:00','mm/dd/yyyy hh24:mi');
stop_week := -1;
dst_stop := to_date('10/31/'||year_part||' 02:00','mm/dd/yyyy hh24:mi');
ElsIf year_part = 1975 Then -- 1975 Trial.
dst_msg := '1975 Trial of Extended DST. ';
--dst_msg := dst_msg || 'Spring Forward 2:00 AM Feb 23 (skip 02:00:00 through 02:59:59, I.E. skip from 01:59:59 to 03:00:00). ';
--dst_msg := dst_msg || 'Fall Back 2:00 AM Oct 26, the last Sun in Oct (repeat 02:00:00 to 02:59:59, I.E. jump back from 02:59:59 to 02:00:00 once). ';
DBMS_OUTPUT.PUT_LINE(' '||dst_msg);
dst_start := to_date('02/23/1975 02:00','mm/dd/yyyy hh24:mi');
dst_stop := to_date('10/26/1974 02:00','mm/dd/yyyy hh24:mi');
Goto found_start_stop;
ElsIf year_part = 1974 Then -- 1974 Trial.
dst_msg := '1974 Trial of Extended DST. ';
--dst_msg := dst_msg || 'Spring Forward 2:00 AM Jan 6 (skip 02:00:00 through 02:59:59, I.E. skip from 01:59:59 to 03:00:00)). ';
--dst_msg := dst_msg || 'Fall Back 2:00 AM Oct 27 (repeat 02:00:00 to 02:59:59, I.E. jump back from 02:59:59 to 02:00:00 once). ';
DBMS_OUTPUT.PUT_LINE(' '||dst_msg);
dst_start := to_date('01/06/1974 02:00','mm/dd/yyyy hh24:mi');
dst_stop := to_date('10/27/1974 02:00','mm/dd/yyyy hh24:mi');
Goto found_start_stop;
ElsIf year_part >= 1961 Then -- 1961 thru 1973 First National DST Standard.
dst_msg := '1961 thru 1973: First National DST Standard. ';
--dst_msg := dst_msg || 'Spring Forward 2:00 AM last Sunday in April (skip 02:00:00 through 02:59:59, I.E. skip from 01:59:59 to 03:00:00). ';
--dst_msg := dst_msg || 'Fall Back 2:00 AM last Sunday in October (repeat 02:00:00 to 02:59:59, I.E. jump back from 02:59:59 to 02:00:00 once). ';
start_week := -1;
dst_start := to_date('04/30/'||input_date||' 02:00','mm/dd/yyyy hh24:mi');
stop_week := -1;
dst_stop := to_date('10/31/'||year_part||' 02:00','mm/dd/yyyy hh24:mi');
ElsIf year_part >=1900 Then -- DST was applied inconsistently or not at all
dst_msg := 'N/A. Before 1961, DST was applied inconsistently across states or not at all. Standard Time returned. ';
Goto found_start_stop;
ElsIf year_part < 1900 Then -- Invalid year_part
dst_msg := 'N/A. DST never active before 1900';
Goto found_start_stop;
Else -- Invalid year_part
dst_msg := 'N/A. Error. Invalid datetime value.';
Goto found_start_stop;
End If;
DBMS_OUTPUT.PUT_LINE(' The code specified the following DST rules for the input date ('||input_date||'). '||dst_msg);
if start_week > 0 then
DBMS_OUTPUT.PUT_LINE(' Start on '||dow_list(dst_dow)||' #'||start_week||' of '||trunc(dst_start,'W')||'. ');
else
DBMS_OUTPUT.PUT_LINE(' Starts '||start_week||' from the last '||dow_list(dst_dow)||' of '||trunc(dst_start,'W')||'. ');
end if;
if stop_week > 0 then
DBMS_OUTPUT.PUT_LINE(' End on '||dow_list(dst_dow)||' #'||stop_week||' of '||trunc(dst_stop,'W')||'. ');
else
DBMS_OUTPUT.PUT_LINE(' Ends '||stop_week||' from the last '||dow_list(dst_dow)||' of '||trunc(dst_stop,'W')||'. ');
end if;
DBMS_OUTPUT.PUT_LINE(' ');
/* Apply formula determined above to find dst start and stop times for the year of the input_date.
This section is skipped if start/stop already determined or indeterminant.
*/
-- DstStartDay
inc_dec := start_week/abs(start_week); -- results in +1 or -1
Cnt := 0; i:=0;
while (Cnt < abs(start_week) and i<20) loop
i:=i+1;
if (to_char(dst_start,'D') = dst_dow) then
Cnt := Cnt + 1;
--DBMS_OUTPUT.PUT_LINE(' Found '||dow_list(dst_dow))||' '||Cnt||': '||dst_start)
end if;
if (Cnt < abs(start_week)) then
dst_start := dst_start + inc_dec;
end if;
end loop;
case inc_dec
when 1 then
DBMS_OUTPUT.PUT_LINE(' Spring forward on '||dow_list(dst_dow)||' #'||Cnt||' of the month: '||dst_start);
else
DBMS_OUTPUT.PUT_LINE(' Spring forward on the last'||dow_list(dst_dow)||'of the month: '||dst_start);
end case;
-- DstStopDay
inc_dec := stop_week/abs(stop_week); -- results in +1 or -1
Cnt := 0; i :=0;
while (Cnt < abs(stop_week) and i <20) loop -- to_char(dst_stop,'D') > 1 loop
i:=i+1;
if (to_char(dst_stop,'D') = dst_dow) then
dst_stop := dst_stop + inc_dec;
Cnt := Cnt + 1;
end if;
if (Cnt < abs(stop_week)) then
dst_stop := dst_stop + inc_dec;
end if;
end loop;
case inc_dec
when 1 then
DBMS_OUTPUT.PUT_LINE(' Fall back on '||dow_list(dst_dow)||' #'||Cnt||' of the month: '||dst_stop);
else
DBMS_OUTPUT.PUT_LINE(' Fall back on the last'||dow_list(dst_dow)||'of the month: '||dst_stop);
end case;
<<found_start_stop>>
dst_range(1) := dst_start;
DBMS_OUTPUT.PUT_LINE(' dst_range(1): '||to_char(dst_range(1),'mm/dd/yyyy hh24:mi')||' = '||dst_start);
dst_range(2) := dst_stop;
DBMS_OUTPUT.PUT_LINE(' dst_range(2): '||to_char(dst_range(2),'mm/dd/yyyy hh24:mi')||' = '||dst_stop);
DBMS_OUTPUT.PUT_LINE(' ** Finish: dst_start_stop Func **');
Return dst_range;
END dst_start_stop;
Function is_dst_now
Return boolean
AS
--type date_array is table of date;
dst_range date_array;
curr_time date := LocalTimestamp;
Begin
dst_range := date_array();
dst_range.extend(2);
dst_range := dst_start_stop(curr_time);
If (dst_range(1) <= curr_time and curr_time < dst_range(2)) then
DBMS_OUTPUT.PUT_LINE('DST is active.');
Return True;
Else
DBMS_OUTPUT.PUT_LINE('DST is NOT active.');
Return False;
End If;
End;
FUNCTION dst_offset (prevailing_date DATE, dst_start DATE, dst_stop DATE)
RETURN number
AS
offset_days number :=0;
BEGIN
DBMS_OUTPUT.PUT_LINE(' Starting dst_offset sub-function:');
DBMS_OUTPUT.PUT_LINE(' where (input date, DST start, DST stop) = '||to_char(prevailing_date,'mm/dd/yyyy hh24:mi')
||', '||to_char(dst_start,'mm/dd/yyyy hh24:mi')||', '||to_char(dst_stop,'mm/dd/yyyy hh24:mi'));
If (dst_start <= prevailing_date and prevailing_date < dst_stop) then
offset_days :=1/24;
DBMS_OUTPUT.PUT_LINE(' input date is between dst start and stop');
Else
offset_days :=0;
DBMS_OUTPUT.PUT_LINE(' input date is not between dst start and stop');
End If;
DBMS_OUTPUT.PUT_LINE(' Result: DST Offset days = '||offset_days);
DBMS_OUTPUT.PUT_LINE(' hours = '||(offset_days*24));
Return offset_days;
END dst_offset;
-- Begin --move this down under the function -- ******************
FUNCTION Convert_TZ (input_date DATE, input_tz varchar2, output_tz varchar2)
RETURN date
AS
-- Variables
input_sz varchar(3) := substr(input_TZ,1,1)||'S'||substr(input_TZ,3,1);
input_sz varchar(3) := substr(output_TZ,1,1)||'S'||substr(output_TZ,3,1);
temp_str varchar2(1000);
dst_range date_array;
input_dst_offset number := 0;
input_tz_offset number := 0;
input_date_st date; --standard time
gmt_date date;
output_dst_offset number := 0;
output_tz_offset number := 0;
output_date date;
output_date_pt date; -- prevailing time
tz_offset_str varchar2(30);
--orig_nls_date_format varchar2(30) := NLS_DATE_FORMAT;
--TempYear number(4,0) := to_char(TempDate,'YYYY'); -- or := trunc(PrevailingTime, YYYY);
BEGIN
DBMS_OUTPUT.PUT_LINE('Starting Pl/sql procedure. ');
DBMS_OUTPUT.PUT_LINE('Input Date: '||to_char(input_date,'mm/dd/yyyy hh24:mi')||' '||input_tz||'. ');
-- Find DST start/stop dates
dst_range := date_array();
dst_range.extend(2);
dst_range := dst_start_stop(input_date);
DBMS_OUTPUT.PUT_LINE('DST date range determined. ');
DBMS_OUTPUT.PUT_LINE(' dst_range(1): '||to_char(dst_range(1),'mm/dd/yyyy hh24:mi')||' = '||dst_range(1));
DBMS_OUTPUT.PUT_LINE(' dst_range(2): '||to_char(dst_range(2),'mm/dd/yyyy hh24:mi')||' = '||dst_range(2));
-- Convert Input Date from input time zone to GMT
If upper(input_TZ) in ('GMT','UCT') then
-- If input TZ is GMT, we can skip this conversion!
DBMS_OUTPUT.PUT_LINE(' Input Time is ('||to_char(input_date,'mm/dd/yyyy hh24:mi')||' '
||input_tz||' GMT). No conversion required. ');
input_tz_offset := 0;
input_dst_offset := 0;
gmt_date := input_date;
Else
-- Convert from local prevailing to local standard time
-- Get input_dst_offset
Case upper(substr(input_TZ,2,1))
When 'S' then
-- already in standard time, not conversion needed.
input_dst_offset := 0; -- duplicative
DBMS_OUTPUT.PUT_LINE('Standard time ('||input_tz||') entered; no dst offset.' );
--input_tz_offset := input_tz_offset;
Else
-- run dst_offset function to convert from prevailing or daylight time to standard time.
input_dst_offset := dst_offset(input_date, dst_range(1), dst_range(2));
input_date_st := input_date - input_dst_offset;
DBMS_OUTPUT.PUT_LINE('Daylight Saving Time Effective ('||to_char(input_date,'mm/dd/yyyy hh24:mi')||' '
||input_tz||'); 1 hour offset; input DST offset = '||input_dst_offset);
DBMS_OUTPUT.PUT_LINE(' where (input_date, dst_start, dst_stop) = '
||to_char(input_date,'mm/dd/yyyy hh24:mi')
||' '||input_tz||', '||dst_range(1)||', '||dst_range(2)||', ');
DBMS_OUTPUT.PUT_LINE(' which adjusts '||to_char(input_date,'mm/dd/yyyy hh24:mi')||' '||input_tz
||' daylight to '||input_date_st||' standard time. ');
End Case;
-- Convert from local standard time to GMT
SELECT TZ_OFFSET((SELECT max(tzname) FROM V$TIMEZONE_NAMES where tzabbrev = input_TZ))
INTO tz_offset_str
FROM DUAL;
input_tz_offset := ( substr(tz_offset_str,1,3)/24 + substr(tz_offset_str,5,2)/1440 );
If is_dst_now then
input_tz_offset := input_tz_offset - 1/24;
End if;
DBMS_OUTPUT.PUT_LINE(' input_tz_offset (fractional days): '||input_tz_offset||'. ');
DBMS_OUTPUT.PUT_LINE(' input_tz_offset (hours): '||input_tz_offset*24||'. ');
gmt_date := input_date_st - input_tz_offset;
End If;
-- Convert input date from GMT to requested output time zone
DBMS_OUTPUT.PUT_LINE(' ');
DBMS_OUTPUT.PUT_LINE('Starting output_date analysis. ');
If upper(output_TZ) in ('GMT','UCT') then
-- If desired output TZ is GMT, we can skip this conversion!
output_tz_offset := 0;
output_dst_offset := 0;
output_date := gmt_date;
DBMS_OUTPUT.PUT_LINE(' Requested output format is GMT: ('||to_char(output_date,'mm/dd/yyyy hh24:mi')||' '||output_tz||'). No conversion required. ');
Else
-- Get output_dst_offset
Case upper(substr(output_TZ,2,1))
When 'S' then
output_dst_offset := 0; -- duplicative
DBMS_OUTPUT.PUT_LINE('Standard time ('||output_TZ||') entered; no dst offset.' );
Else
output_dst_offset := dst_offset(gmt_date + output_tz_offset, dst_range(1), dst_range(2));
End Case;
-- Convert from GMT to local standard time
SELECT TZ_OFFSET((SELECT max(tzname) FROM V$TIMEZONE_NAMES where tzabbrev = output_TZ)) INTO tz_offset_str FROM DUAL;
output_tz_offset := ( substr(tz_offset_str,1,3)/24 + substr(tz_offset_str,5,2)/1440 );
DBMS_OUTPUT.PUT_LINE(' output_tz_offset (fractional days): '||output_tz_offset||'. ');
DBMS_OUTPUT.PUT_LINE(' output_tz_offset (hours): '||output_tz_offset*24||'. ');
If is_dst_now then
output_tz_offset := output_tz_offset - 1/24;
DBMS_OUTPUT.PUT_LINE(' tz_offset correction... ');
DBMS_OUTPUT.PUT_LINE(' output_tz_offset (fractional days): '||output_tz_offset||'. ');
DBMS_OUTPUT.PUT_LINE(' output_tz_offset (hours): '||output_tz_offset*24||'. ');
End if;
output_date := gmt_date + output_tz_offset + output_dst_offset;
DBMS_OUTPUT.PUT_LINE(' gmt_date: '||gmt_date);
DBMS_OUTPUT.PUT_LINE(' output_tz_offset: '||output_tz_offset);
DBMS_OUTPUT.PUT_LINE(' output_dst_offset: '||output_dst_offset);
DBMS_OUTPUT.PUT_LINE('Daylight Saving Time ('||output_TZ||') offset = '||output_dst_offset);
DBMS_OUTPUT.PUT_LINE(' where (output_date, dst_start, DST_stop) = '||output_date||', '||dst_range(1)||', '||dst_range(2));
DBMS_OUTPUT.PUT_LINE(' which adjusts '||output_date||' standard to '||output_date_pt||' daylight time. ');
End If;
DBMS_OUTPUT.PUT_LINE('Output Date = '||to_char(output_date,'mm/dd/yyyy hh24:mi')||' '||output_tz||'. ');
Goto AllDone;
<<FoundError>>
<<AllDone>>
DBMS_OUTPUT.PUT_LINE(' ');
DBMS_OUTPUT.PUT_LINE('*** Results ***');
DBMS_OUTPUT.PUT_LINE(' ');
if input_dst_offset <> 0 then
temp_str := 'daylight saving';
else
temp_str := 'standard';
end if;
DBMS_OUTPUT.PUT_LINE(' Input Date: '||to_char(input_date,'mm/dd/yyyy hh24:mi')||' '||input_tz||', which falls in '||temp_str||' time. ');
DBMS_OUTPUT.PUT_LINE(' GMT Date: '||to_char(gmt_date,'mm/dd/yyyy hh24:mi')||' UTC/GMT. ');
DBMS_OUTPUT.PUT_LINE(' Output Date: '||to_char(output_date,'mm/dd/yyyy hh24:mi')||' UTC/GMT. ');
if output_dst_offset <> 0 then
temp_str := 'daylight saving';
else
temp_str := 'standard';
end if;
DBMS_OUTPUT.PUT_LINE(' All Done. Return Value: '||to_char(output_date,'mm/dd/yyyy hh24:mi')||' '||output_tz||'. ');
DBMS_OUTPUT.PUT_LINE(' ');
DBMS_OUTPUT.PUT_LINE('*** End of Results ***');
DBMS_OUTPUT.PUT_LINE(' ');
DBMS_OUTPUT.PUT_LINE('LocalTimestamp EPT: '||LocalTimestamp);
DBMS_OUTPUT.PUT_LINE('LocalTimestamp GMT:'||LOCALTIMESTAMP at time zone '+00:00');
Return output_date;
END;
/*********************** End of Declarations of Variables and Functions for Time Zone Conversion (Convert_TZ function) *********************/
Begin
/*********************** Start of Procedural Code for Time Zone Conversion (Convert_TZ function) *********************/
/* DOW list is required for Time Zone Conversion (Convert_TZ function) and should not be deleted. */
dow_list := str_array();
dow_list.extend(7);
dow_list(1) := 'Sun';
dow_list(2) := 'Mon';
dow_list(3) := 'Tue';
dow_list(4) := 'Wed';
dow_list(5) := 'Thu';
dow_list(6) := 'Fri';
dow_list(7) := 'Sat';
/* Next 2 lines are example of use of Time Zone Conversion (Convert_TZ function). */
return_date := Convert_TZ (input_date, input_tz, output_tz);
DBMS_OUTPUT.PUT_LINE('ta-dah! '||return_date);
/*********************** End of Procedural Code for Time Zone Conversion (Convert_TZ function) *********************/
-- ******** User coded begins here ******** --
End;

Answer 7

RTRIM( TO_CHAR( systimestamp at time zone 'GMT', 'DD-MON-YYYY HH24:MI:SS TZR' ))
RTRIM( TO_CHAR( systimestamp at time zone 'EST', 'DD-MON-YYYY HH24:MI:SS TZR' ))
RTRIM( TO_CHAR( systimestamp at time zone 'PST', 'DD-MON-YYYY HH24:MI:SS TZR' ))
output:
05-NOV-2014 17:20:10 GMT
05-NOV-2014 12:20:10 EST
05-NOV-2014 09:20:10 PST
substr('05-NOV-2014 09:20:10 PST', -3, 3) will return 'PST'
RTRIM (EXTRACT (HOUR from systimestamp ))
output: 17 (notice the 17 is in GMT time)