Returns an integer value representing the number of days from January 1, 4713 B.C. (the start of the Julian date calendar) to the date value specified in the argument.

The schema is SYSFUN.

expression

An expression that returns a value of one of the following built-in data types:
a DATE, TIMESTAMP, or a valid character string representation of a date or timestamp that is not a CLOB.
In a Unicode database, if a supplied argument is a graphic string, it is first converted to a character string before the function is executed.

The result of the function is INTEGER.
The result can be null; if the argument is null, the result is the null value.