a is a date value or an alphanumeric value that matches the current date format

This date value

a is an alphanumeric value that does not match the current date format

Error message

ais a timestamp value or an alphanumeric value that matches the current timestamp format

The date value that is part of the timestamp

a is a fixed point or floating point number

Date value that is equal to the xth day after 31.12.0000 (x=TRUNC(a))

a is a NULL value

NULL value

a is a special NULL value

Error message