Regular Expression for Date Format DD-MON-YYYY HH24:MI:SS

Use below regular expression to validate if given string is in specific date format.

select COUNT(1)  from DUAL where regexp_like('12-JUN-2016 23:34:59','^(\d){2}-[A-Z]{3}-(\d){4}\s(\d){2}:(\d){2}:(\d){2}$')
1

select COUNT(1)  from DUAL where regexp_like('121-JUN-2016 23:34:59','^(\d){2}-[A-Z]{3}-(\d){4}\s(\d){2}:(\d){2}:(\d){2}$')
0


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^          : Starting String
$          : Ending String
{n}      : Execute last rule n time
[A-Z]   : All CAP Alphabets check
\d         :  digit check
\s          : Space