Returns the number of years in a duration.
fn:years-from-duration( $arg as xs:duration?xs:integer?If $arg is the empty sequence, the function returns the empty sequence.
Otherwise, the function returns an xs:integer representing the years
component in the value of $arg. Given that a duration
is a ($months, $seconds) tuple, the result is the value of ($months idiv 12)
.
If $arg is a negative duration then the result will be negative.
If $arg is an xs:dayTimeDuration the function returns 0.
The expression fn:years-from-duration(xs:yearMonthDuration("P20Y15M")) returns 21.
The expression fn:years-from-duration(xs:yearMonthDuration("-P15M")) returns -1.
The expression fn:years-from-duration(xs:dayTimeDuration("-P2DT15H")) returns 0.