In the old RPi image the ntp server was not working after installing it. In the OMV 3.x Debian armhf image it does work. So the part in the old guide on the ntp server can be skipped. I just had to modify 3 files and install i2c-tools to get the RTC module recognized by the system. I will give the file edits now.
With this file all you have to do is add this line at the end of the file and save it:
Add the following line to the end of this file and save it.
After making those changes:
apt-get install i2c-tools
Then turn off your rpi, "shutdown -h now", and install your RTC module. See old guide via link above for more info. on correct pins if needed. If your rpi already has the RTC module installed you can reboot instead, "shutdown -r now".
After reboot, or starting, your RPi should now recognize the RTC module. You can check with this command:
i2cdetect -y 1