TO_CHAR (datetime)
                                                            Purpose
This function converts a date, timestamp or interval into a string.
Syntax
to_char (datetime)::=
                                                                        
                                                                    
Usage Notes
- The standard format is used if no format is specified, this is defined in session parameter ALTER SESSION or ALTER SESSION.
 - For information, refer to the Date/time format models.
 - By the optional third parameter you can specify the language setting for the format (for example, NLS_DATE_LANGUAGE).
 - Supported languages are German (
DEU,DEUTSCHorGERMAN) and English (ENGorENGLISH). - For data type 
TIMESTAMP WITH LOCAL TIME ZONEthis function is calculated within the session time zone. - Results for variable-length format masks such as 
MONTHandDATEwill be padded with spaces to their longest possible value. 
Example
SELECT TO_CHAR(DATE '1999-12-31') TO_CHAR;
SELECT TO_CHAR(TIMESTAMP '1999-12-31 23:59:00',
               'HH24:MI:SS DD-MM-YYYY') TO_CHAR;
SELECT TO_CHAR(DATE '2013-12-16',
               'DD. MON YYYY',
               'NLS_DATE_LANGUAGE=DEU') TO_CHAR;