#!/bin/bash
DATE1=$(/usr/gnu/bin/date +"%Y-%m-%d-%R")
DATE2=$(/usr/gnu/bin/date --date='1 month ago' +"%Y-%m-%d-%R")
/usr/sbin/zfs snapshot tank@$DATE1
/usr/sbin/zfs destroy tank@$DATE2

Can't exec /bin/bash at line 1.