I think this is not what you are looking for, but, just for the record:
:%!awk -F: '{a=$2*60+$1} END {printf("\%d:\%d",a/60,a\%60)}' I think this is not what you are looking for, but, just for the record:
:%!awk -F: '{a=$2*60+$1} END {printf("\%d:\%d",a/60,a\%60)}'