Minor Description
These functions are needed for enabling convenient conversion of binary date/time data into xs:date, xs:time, or xs:dateTime types.
dfdlx:date($year as AnyAtomicType, $month as AnyAtomicType, $day as AnyAtomicType): xs:date dfdlx:time($hour as AnyAtomicType, $minute as AnyAtomicType, $second as AnyAtomicType): xs:time
Variations of the time constructor that also allow for timezone information, fractional seconds are possibly needed, but the above, along with the two arg fn:dateTime constructor (see DAFFODIL-2669) already defined by DFDL, enable constructing an xs:dateTime type from a bunch of binary components giving each part of the dateTime.
fn:dateTime($arg1 as xs:date, $arg2 as xs:time) as xs:dateTime
The alternative is you have to clumsily create a string that looks like an iso dateTime, and then feed that to xs:dateTime constructor.