Oracle TO_DATE format, symbol for "any character" - oracle

Question

In this answer the following query is suggested:
SELECT TO_DATE(
'Thu Nov 24 15:20:52 CET 2016',
'DY MON DD HH24:MI:SS "CET" YYYY'
)
FROM DUAL
¿ there are some character to be used in the format with the meaning of "any" ? I like replace "CET" in the format string by something like "..." or "###", that is:
'DY MON DD HH24:MI:SS ... YYYY'
One example, ¿ which format will accept all the following date strings :
2017-12-31
2017_12_31
2017x12x31

Answer 1

You can extract relevant part by regular expression.
select
TO_DATE(
regexp_substr('Thu Nov 24 15:20:52 CET 2016', '^.+\d{2}:\d{2}:\d{2}')
||regexp_substr('Thu Nov 24 15:20:52 CET 2016', ' \d{4}$'),
'DY MON DD HH24:MI:SS YYYY')
from dual;
or
select
TO_DATE(
REGEXP_REPLACE('Thu Nov 24 15:20:52 CET 2016', '\w+ (\d{4})$', '\1'),
'DY MON DD HH24:MI:SS YYYY')
from dual;

Answer 2

Here's another way using to_timestamp_tz:
WITH sample_data AS (SELECT 'Thu Nov 24 15:20:52 CET 2016' str FROM dual UNION ALL
SELECT 'Fri Dec 11 23:16:39 PST 2015' str FROM dual)
SELECT str,
to_timestamp_tz(str, 'Dy Mon dd hh24:mi:ss TZR yyyy', 'nls_date_language = english') timestamp_at_orig_tz,
CAST(to_timestamp_tz(str, 'Dy Mon dd hh24:mi:ss TZR yyyy', 'nls_date_language = english') AS DATE) dt,
CAST(to_timestamp_tz(str, 'Dy Mon dd hh24:mi:ss TZR yyyy', 'nls_date_language = english') AT TIME ZONE '-5:00' AS DATE) dt_at_utc_minus_5,
cast(sys_extract_utc(to_timestamp_tz(str, 'Dy Mon dd hh24:mi:ss TZR yyyy', 'nls_date_language = english')) AS DATE) dt_at_utc
FROM sample_data;
STR TIMESTAMP_AT_ORIG_TZ DT DT_AT_UTC_MINUS_5 DT_AT_UTC
---------------------------- -------------------------------- ------------------- ------------------- -------------------
Thu Nov 24 15:20:52 CET 2016 24-NOV-16 15.20.52.000000000 CET 24/11/2016 15:20:52 24/11/2016 09:20:52 24/11/2016 14:20:52
Fri Dec 11 23:16:39 PST 2015 11-DEC-15 23.16.39.000000000 PST 11/12/2015 23:16:39 12/12/2015 02:16:39 12/12/2015 07:16:39
I've given a three different ways of converting the timestamp-as-a-string into a date:
Convert the timestamp as is into a date. Note that this will lose any timestamp information you have - useful if you really don't care about timezone information.
Convert the timestamp into a specific timezone (in my example, UTC - 5) before converting it into a date.
Convert the timestamp into UTC before converting it into a date (you can use the previous method to do this, but sys_extract_utc() is a little more self-explanatory, IMHO, which can only aid readability and maintainability!).
With your updated question (which seems to be more around the date part separator, not the timezone), the following should do the trick:
WITH sample_data AS (SELECT '2017-12-31' dt_str FROM dual UNION ALL
SELECT '2017_12_31' dt_str FROM dual UNION ALL
SELECT '2017x12x31' dt_str FROM dual)
SELECT dt_str,
to_date(regexp_replace(dt_str,
'([[:digit:]]{4}).([[:digit:]]{2}).([[:digit:]]{2})',
'\1-\2-\3'), 'yyyy-mm-dd')
FROM sample_data;
DT_STR DT
---------- ----------
2017-12-31 31/12/2017
2017_12_31 31/12/2017
2017x12x31 31/12/2017