Why is Debian Jessie systemd reloading the Apache server every morning

After upgrading a web server from Debian Wheezy to Debian Jessie, the following log entries appear in the system log every morning. The times vary somewhat, but it seems to always happen at approximately the same time (plus/minus maybe 10-15 minutes at most). Nothing similar (that I can recall) happened before the upgrade.

Oct 23 06:25:02 hostname systemd[1]: Reloading LSB: Apache2 web server.
Oct 23 06:25:04 hostname apache2[1545]: Reloading web server: apache2.
Oct 23 06:25:04 hostname systemd[1]: Reloaded LSB: Apache2 web server.
Oct 23 06:29:10 hostname rsyslogd0: action 'action 17' resumed (module 'builtin:ompipe') [try http://www.rsyslog.com/e/0 ]
Oct 23 06:29:10 hostname rsyslogd-2359: action 'action 17' resumed (module 'builtin:ompipe') [try http://www.rsyslog.com/e/2359 ]

Looking at the output of service apache2 status:

● apache2.service - LSB: Apache2 web server
   Loaded: loaded (/etc/init.d/apache2)
   Active: active (running) since Fri 2015-10-09 21:33:36 UTC; 1 weeks 6 days ago
  Process: 21467 ExecStop=/etc/init.d/apache2 stop (code=exited, status=0/SUCCESS)
  Process: 1545 ExecReload=/etc/init.d/apache2 reload (code=exited, status=0/SUCCESS)
  Process: 21489 ExecStart=/etc/init.d/apache2 start (code=exited, status=0/SUCCESS)
   CGroup: /system.slice/apache2.service
           ├─ 1625 /usr/sbin/apache2 -k start
           ├─ 1626 /usr/sbin/apache2 -k start
           ├─ 4686 /usr/sbin/apache2 -k start
           ├─ 7745 /usr/sbin/apache2 -k start
           ├─ 7746 /usr/sbin/apache2 -k start
           ├─ 7747 /usr/sbin/apache2 -k start
           ├─ 7748 /usr/sbin/apache2 -k start
           ├─ 7753 /usr/sbin/apache2 -k start
           ├─ 7760 /usr/sbin/apache2 -k start
           ├─ 7771 /usr/sbin/apache2 -k start
           └─21505 /usr/sbin/apache2 -k start

Oct 21 06:25:02 hostname.fqdn systemd[1]: Reloading LSB: Apache2 web server.
Oct 21 06:25:08 hostname.fqdn apache2[32200]: Reloading web server: apache2.
Oct 21 06:25:08 hostname.fqdn systemd[1]: Reloaded LSB: Apache2 web server.
Oct 22 06:25:03 hostname.fqdn systemd[1]: Reloading LSB: Apache2 web server.
Oct 22 06:25:05 hostname.fqdn apache2[16779]: Reloading web server: apache2.
Oct 22 06:25:05 hostname.fqdn systemd[1]: Reloaded LSB: Apache2 web server.
Oct 23 06:25:02 hostname.fqdn systemd[1]: Reloading LSB: Apache2 web server.
Oct 23 06:25:04 hostname.fqdn apache2[1545]: Reloading web server: apache2.
Oct 23 06:25:04 hostname.fqdn systemd[1]: Reloaded LSB: Apache2 web server.
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

I'm not sure if I'm looking in the right place, the only part of /run/systemd/generator.late/apache2.service that looks remotely relevant is the mention of the ExecReload command, which is echoed in the service apache2 status output.

Why is systemd reloading the web server with such regularity, despite nobody doing anything on the server, and how do I make it stop?