Maybe using with exec this will be a bit nicer than:

mango:~# service atop status
● atop.service - "advanced system & process monitor"
   Loaded: loaded (/lib/systemd/system/atop.service; disabled)
   Active: active (running) since Di 2014-09-16 16:24:17 CEST; 2min 54s ago
     Docs: man:atop(1)
 Main PID: 30343 (sh)
   CGroup: /system.slice/atop.service
           ├─30343 /bin/sh -c /usr/bin/atop -a -R -w /var/log/atop/atop_$(date +%Y%m%d) 600
           └─30345 /usr/bin/atop -a -R -w /var/log/atop/atop_20140916 600
Use service atop restart since it works natively with systemd and sysvinit.