Question

I need your help in understanding the below query.

   SELECT To_date(To_char(( ( To_timestamp_tz(From_tz(Cast(l_end_date AS TIMESTAMP)
                                           ,
                                                  dbtimezone))
                                        ) AT
                                        TIME
                                                ZONE ( l_time_zone ) ),
                      'YYYY-MM-DD HH24:MI:SS'
               ), 'YYYY-MM-DD HH24:MI:SS')
FROM   dual
where l_end_date = 31-Dec-2018

Answer 1

Well, ultimately it converts the date 31-Dec-2018 at midnight into whatever local timezone date you indicate with l_time_zone. E.g., for me with dbtimezone = +00:00 and l_time_zone set to Australia/Sydney I get 31/12/2018 11:00:00 AM.

But to fully understand you may just want to look at each function’s documentation:

• DBTIMEZONE
• TO_TIMESTAMP_TZ
• FROMTZ
• TO_DATE
• TO_CHAR
• AT TIME ZONE