Re: Tried that.... no success
mysqldump test | gzip > /tmp/mydb_`date '+ %d_%m_%y__%H-%M'`.sql.gz
bash: /tmp/mydb_`date '+ %d_%m_%y__%H-%M'`.sql.gz: ambiguous redirect
Well, it works for me, at least on command-line. I haven't tried that via "call".