I came here looking for why the crontab-scheduled job was running at the incorrect day (esxi 5.1). Note that I had no parsing errors, and the process of using /etc/rc.local.d/local.sh to add the necessary entries to root's crontab worked as designed.
relevant contents of /var/spool/cron/crontabs/root
30 01 * * 7 /vmfs/volumes/backupstore0/ghettoVCB/ghettoVCB.sh ... etc...
Unexpectedly, the job ran on Thursday at 1:30 am.
I suspect there is some difference in the implementation of the busybox cron/crontab that doesn't recognize the almost universal convention that sunday is either 0 or 7
I am going to put "sun" (no quotes) in the DOW column. If it works, no further postings from me will confirm that meristema has the correct answer to my problem (which is not the issue of the OP was having).