EXTEND( )

The EXTEND( ) operator converts an expression that returns a DATETIME or DATE value to a DATETIME value of a specified precision and scale.

The EXTEND( ) operator returns the value of its DATE or DATETIME operand, but with an adjusted precision that you can specify by a DATETIME qualifier. The operand can be a time expression of any valid precision. If it is a character string, it must consists of valid and unambiguous time unit values and separators, but with these restrictions:

It cannot be a string constant in DATE format, such as "12/12/93".

It cannot be an ambiguous numeric DATETIME value, such as "05:06" or "05-06" whose time units are ambiguous.

It cannot be a time expression that returns an INTERVAL value.

Reference

UNITS