at: Run a one-time command at a specific time

"at" executes commands at a specified time. You may need to install the "at" package manually.

# install
$ sudo apt-get install at

# start
$ sudo atd

$ at 00:05
at> echo "123" > /tmp/test.txt

$ at 00:05 31.12.2016
at> DPS_ENV=production /home/ubuntu/.virtualenvs/dps-py3/bin/python /home/ubuntu/dps/manage.py send_withdraw_emails 2016 12 > /tmp/send_withdraw_emails.log

ref:
https://www.lifewire.com/linux-command-at-4091646
http://tecadmin.net/one-time-task-scheduling-using-at-commad-in-linux/