The only posibility i see is to delete directly in ECS database existing YEAR or CALENDAR.
It will be exactly the same using Control-M Desktop utility.
To Control-EM 6.1.03 there is some SQL commands :
To delete a Year in a existing Calendar
delete from DF_YEARS where DATA_CENTER='DATACENTER' and CALENDAR='CALENDAR' and YEAR='YEAR'
To delete a Calendar
Delete al YEAR for that calendar
delete from DF_YEARS where DATA_CENTER='DATACENTER' and CALENDAR='CALENDAR'
and the Calendar itself
delete from DF_CALENDAR where DATA_CENTER='DATACENTER' and CALENDAR='CALENDAR'
Dont' forget, if you delete definitively a YEAR or a CALENDAR under ECS you need to do exactly the same on your Control-M Server.
The table is CMS_DATEMM using CALNAME and JOBYEAR fields.