Accurate time keeping is important on any larger network. Fx Active Directory needs accurate time for logins to work properly. But "Domain Time II" isn't the only way to accomplish this.
In a modern Active Directory environment, there is basic but working time synchronization already built in.
For non-Windows devices (switches, routers, appliances) you can use the NTP protocol. You can leverage your existing investment in "Domain Time II" by using it as an NTP server for your non-Windows devices, or you could set up a Linux/BSD server with NTPd.
Be sure to set the clock of your root time server from a trusted source. The common solution there would be 3 or 5 upstream NTP servers from pool.ntp.org .
The built-in Active Directory time sync isn't that accurate -- generally it syncs better than +/- 1 second, and often a few hundred milliseconds. Domain Time II is probably more accurate than that. So it really comes down to how much precision you need, and which platform you're more comfortable with/know best.