You might want to change systemd to systemctl for Debian systems.
Comments on How to schedule Folding@home to only run during winter nights
Thanks, Jim. It’s supposed to be systemctl everywhere.
Much simpler. Add 2 lines to /etc/crontab like:
00 6 * 9-3 * root /usr/bin/FAHClient --send-unpause
15 1 * 9-3 * root /usr/bin/FAHClient --send-pause
Jim