Hi,
you can tune initial search filters modifiying URL used to access Calendar tab,
go to role management > web forms, then find Change Calendar tab and modify URL, supported URL variable (operators) could be found here: Supported Server Operations - CA Service Management - 14.1 - CA Technologies Documentation
for example you can add:
+QBE.NN.sched_start_date=null
to display only changes with filled scheduled start date attribute.
Regards,
cdtj