In ../../../libIGCM/libIGCM_config/libIGCM_config.ksh
L406 
old
        (( PeriodLengthInDays  = PeriodLengthInDays + $( IGCM_date_DaysInMonth $year $(( 10#${month} + ${i} - 12 )) ) ))
new
        (( PeriodLengthInDays  = PeriodLengthInDays + $( IGCM_date_DaysInMonth $(( year + 1 )) $(( 10#${month} + ${i} - 12 )) ) ))