How to derive 0FISCYEAR, 0FISCPER & 0FISCPER3 from 0CALMONTH?

Use formulas in the update rules which are avilable under TIME CHARs.

Go to your update Rules > select Time Chars

Code For 0FISCPER

* fill the internal table "MONITOR", to make monitor entries
data: l_fiscper type rsfiscper.

call function 'FISCPER_FROM_CALMONTH_CALC'
exporting
iv_calmonth = COMM_STRUCTURE-calmonth
iv_periv = 'K4'
importing
ev_fiscper = l_fiscper.

* result value of the routine
RESULT = l_fiscper.

Code for 0FISCPER3

data: l_fiscper3 type t009b-poper.

call function 'FISCPER_FROM_CALMONTH_CALC'
exporting
iv_calmonth = COMM_STRUCTURE-calmonth
iv_periv = 'K4'
importing
ev_fiscper3 = l_fiscper3.

* result value of the routine
RESULT = l_fiscper3.

Code for 0FISCYEAR

data: l_fiscyear type t009b-bdatj.

call function 'FISCPER_FROM_CALMONTH_CALC'
exporting
iv_calmonth = COMM_STRUCTURE-calmonth
iv_periv = 'K4'
importing
ev_fiscyear = l_fiscyear.

* result value of the routine
RESULT = l_fiscyear.

Just copy and paste the code in your system. 
Note: K4 is the Variant. Change Variant according to your requirement.

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