When Installing PKI Hub the installation process automatically configures the built-in chrony service to use the NTP server provided by DHCP. 

In multi-node installations, all the nodes must have synchronized dates to prevent communication errors.

To modify this default configuration, update the chrony configuration file in all the installation nodes. 

/etc/chrony.conf

This configuration file supports multiple NTP sources. For example, you can define individual NTP servers:

server tsa-ntp1.corp.example.com iburst prefer
server tsa-ntp2.corp.example.com iburst
server tsa-ntp3.corp.example.com iburst

You can also configure NTP pools:

pool ntp-pool-primary.corp.example.com iburst maxsources 3
pool ntp-pool-secondary.corp.example.com iburst maxsources 2

Do not modify the following lines under any circumstances.

bindcmdaddress 0.0.0.0
cmdallow all

See a reference of the chrony parameters at https://chrony-project.org/doc/4.4/chrony.conf.html