I recently installed FreeBSD 11.1 on my desktop and wanted to use zfs-tools to create periodic snapshots. Everything related to zfs-tools including my crontab file is setup exactly as another FreeBSD server I run. The only issue on my desktop is that cron does not start, or fails to start during the boot process. If I run
# /etc/rc.d/cron start
then zfs-tools starts taking snapshots as per specified cron times. I am not seeing anything in mail, and AFAIK, /var/log/cron doesn't seem to show anything out of the ordinary.