Here you go:
case("CA_NOTIF_REF_MONTH",'1','January','2','February','3','March','4','April','5','May','6','June','7','July','8','August', '9','September','10','October','11','November','12','December','OTHER')
I have another calculated attribute called CA_NOTIF_REF_MONTH where I take the 2 month char from SAP date field.
Nick