Thanks all.
Quite strange, but since I’ve changed the email where the output goes (Cronjob email per virtual server - #2 by Joe) it seems that it did indeed also run on 0 hour. Strange that it did not mail to the root that time and it did on 1 hour.
Maybe I jumped into conclusions to quick, I will go back testing.
0 hour seems to be just fine, nothing special about it 
Thanks!