A simple code would do..
For example if your AJAHR is coming as "20160831"
Then write code in end routine as:
Loop at result_package assigning <result_fields>.
<result_fields>-calyear = <result_fields>-ajahr+0(4).
endloop.
Else if your AJAHR is coming as "31082016"
Then write code in end routine as:
Loop at result_package assigning <result_fields>.
<result_fields>-calyear = <result_fields>-ajahr+4(4).
endloop.
Similarly you can populate 0CALMONTH as well.
Other simple approach would be to map the AJAHR to a DATE type infoobject in LDP layer and assigning it directly to 0CALYEAR in BT layer
Br,
Maju