systemd-user-sessions.service is used in unit file, so the atd should be

started after almost all services are up and running

at.spec

@@ -194,6 +194,8 @@ fi
 - at-3.1.13-usePOSIXtimers.patch use POSIX timers, so we won't need
   pm-utils hack anymore
 - at-3.1.13-help.patch update usage
+- systemd-user-sessions.service is used in unit file, so the atd should be
+  started after almost all services are up and running
 
 * Thu Jan 12 2012 Fedora Release Engineering <rel-eng@lists.fedoraproject.org> - 3.1.13-7
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_17_Mass_Rebuild

atd.systemd

@@ -1,6 +1,6 @@
 [Unit]
 Description=Job spooling tools
-After=syslog.target
+After=syslog.target systemd-user-sessions.service
 
 [Service]
 EnvironmentFile=/etc/sysconfig/atd