Oracle Time conversion from One Time zone to other

NEW_TIME

The NEW_TIME function converts a date and time from one time zone to another.
Return Value
DATETIME
Syntax
NEW_TIME(datetime-exp this_zone new_zone)
Arguments
this_zone
A text expression that indicates the time zone from which you want to convert datetime-exp. It must be a valid time zone, as listed in the following table.
new_zone
A text expression that indicates the time zone into which you want to convert datetime-exp. It is the time zone of the return value. It must be a valid time zone, as listed in Table 8-1, "Time Zones".
Table 8-1 Time Zones
ASTAtlantic Standard Time
ADT
Atlantic Daylight Time
BST
Bering Standard Time
BDT
Bering Daylight Time
CST
Central Standard Time
CDT
Central Daylight Time
EST
Eastern Standard Time
EDT
Eastern Daylight Time
GMT
Greenwich Mean Time
HST
Alaska-Hawaii Standard Time
HDT
Alaska-Hawaii Daylight Time
MST
Mountain Standard Time
MDT
Mountain Daylight Time
NST
Newfoundland Standard Time
PST
Pacific Standard Time
PDT
Pacific Daylight Time
YST
Yukon Standard Time
YDT
Yukon Daylight Time
Examples
Example 8-33 Using the Current Time of day
The SYSDATE function returns the current date and time to the NEW_TIME function.
SHOW new_time(SYSDATE 'EST' 'PST')
When the date and time in Eastern Standard Time are October 20, 2000, at 1:20 A.M., then the date in Pacific Standard Time, which is three hours earlier, is October 19, 2000. Because SYSDATE uses the format specified by NLS_DATE_FORMAT, which by default only shows the date, the time is not displayed.
19-OCT-00
Example 8-34 Specifying the Time of day
In the following example, the TO_DATE function converts a text string to a valid date and time. The TO_CHAR function includes a date format that temporarily overrides the date format specified by the NLS_DATE_FORMAT option.
SHOW TO_CHAR(NEW_TIME(TO_DATE('11-27-00 22:15:00', 'MM-DD-YY HH24:MI:SS'), -
   'HST' 'PST') 'MM-DD-YY HH24:MI:SS')
This statement converts November 27 at 10:15 P.M. (22:15:00) Alaska-Hawaii Standard Time to November 28 at 12:15 A.M. (00:15:00) Pacific Standard Time. The date format specified in the TO_CHAR function allows the time to be displayed along with the date.
11-28-00 00:15:00
Alternatively, you can change the value of NLS_DATE_FORMAT.
NLS_DATE_FORMAT = 'MM-DD-YY HH24:MI:SS'
Then this statement produces the same result, without requiring the use of TO_CHAR.
SHOW NEW_TIME(TO_DATE('11-27-00 22:15:00', 'MM-DD-YY HH24:MI:SS'), -
   'HST' 'PST')

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