Windows machines might have a Network Time Protocol (NTP) server that's preset in the registry before it's joined to the AWS Managed Microsoft AD domain.
Active Directory (AD) has a built-in NTP server configured on DCs. Modern DCs leverage NTP with backward compatibility support for Simple Network Time ...
It's absolutely fine to use your PDC emulator as a NTP server for non-domain joined computers as long as the PDC gets time from a reliable stratum 1 or stratum ...