Returns the result of subtracting one xs:yearMonthDuration value from
another.
xs:yearMonthDuration values.op:subtract-yearMonthDurations( $arg1 as xs:yearMonthDuration,$arg2 as xs:yearMonthDurationxs:yearMonthDurationThe function returns the result of subtracting the value of $arg2 from the
value of $arg1. The result will be an xs:yearMonthDuration
whose length in months is equal to the length in months of $arg1 minus the
length in months of $arg2.
For handling of overflow, see .
The expression op:subtract-yearMonthDurations(xs:yearMonthDuration("P2Y11M"),
xs:yearMonthDuration("P3Y3M")) returns xs:yearMonthDuration("-P4M").
Either duration (and therefore the result) may be negative.