Returns the month component of an xs:date.
fn:month-from-date( $arg as xs:date?xs:integer?If $arg is the empty sequence, the function returns the empty sequence.
Otherwise, the function returns an xs:integer between 1 and 12, both
inclusive, representing the month component in the local value of $arg.
The expression fn:month-from-date(xs:date("1999-05-31-05:00")) returns 5.
The expression fn:month-from-date(xs:date("2000-01-01+05:00")) returns 1.