* * * * * echo "Test crontab log" > /tmp/crontab.log.$(date --utc +\%Y\%m\%d_\%H\%M\%SZ) 2>&1
ls -lh /tmp | grep log
-rw-rw-r-- 1 ubuntu ubuntu 17 May 4 05:06 crontab.log.20190504_050601Z
-rw-rw-r-- 1 ubuntu ubuntu 17 May 4 05:07 crontab.log.20190504_050701Z