Example:
* * * * * /sbin/btrfs subvolume snapshot -r /your/subvol /snapshot/dir/subvol@auto-minute-$(date +\%Y-\%m-\%d-\%H\%M\%S); /root/btrfs-clean-auto-snapshots.sh /snapshot/dir subvol minute 15
*/15 * * * * /sbin/btrfs subvolume snapshot -r /your/subvol /snapshot/dir/subvol@auto-quarter-$(date +\%Y-\%m-\%d-\%H\%M\%S); /root/btrfs-clean-auto-snapshots.sh /snapshot/dir subvol quarter 4
0 * * * * /sbin/btrfs subvolume snapshot -r /your/subvol /snapshot/dir/subvol@auto-hour-$(date +\%Y-\%m-\%d-\%H\%M\%S); /root/btrfs-clean-auto-snapshots.sh /snapshot/dir subvol hour 24
0 0 * * * /sbin/btrfs subvolume snapshot -r /your/subvol /snapshot/dir/subvol@auto-day-$(date +\%Y-\%m-\%d-\%H\%M\%S); /root/btrfs-clean-auto-snapshots.sh /snapshot/dir subvol day 7
0 0 * * 0 /sbin/btrfs subvolume snapshot -r /your/subvol /snapshot/dir/subvol@auto-week-$(date +\%Y-\%m-\%d-\%H\%M\%S); /root/btrfs-clean-auto-snapshots.sh /snapshot/dir subvol week 4
0 0 1 * * /sbin/btrfs subvolume snapshot -r /your/subvol /snapshot/dir/subvol@auto-month-$(date +\%Y-\%m-\%d-\%H\%M\%S); /root/btrfs-clean-auto-snapshots.sh /snapshot/dir subvol month 3