Datetime Format Templates

A datetime format template is a template that describes the format of datetime data stored in a character string. A format model does not change the internal representation of the value in the database. When you convert a character string into a date, a format model determines how Oracle Database interprets the string. In OLAP DML statements, you can use a format model as an argument of the TO_CHAR and TO_DATE functions to specify:

• The format for Oracle to use to return a value from the database

• The format for a value you have specified for Oracle to store in the database

You can use datetime format templates in the following functions:

• In the TO_* datetime functions to translate a character value that is in a format other than the default format into a datetime value. (The TO_* datetime functions are TO_CHAR, TO_DATE, TO_TIMESTAMP, TO_TIMESTAMP_TZ, TO_YMINTERVAL, and TO_DSINTERVAL.)

• In the TO_CHAR function to translate a datetime value that is in a format other than the default format into a string (for example, to print the date from an application)

The default datetime formats are specified either explicitly with the initialization parameter NLS_DATE_FORMAT or implicitly with the initialization parameter NLS_TERRITORY. You can change the default datetime formats for your session with the ALTER SESSION statement. You can override this default and specify a datetime format for use with a particular OLAP DML object by using the DATE_FORMAT command to add a datetime format to the definition of the object.