Setting an external time source for your domain controller
Asia
w32tm /config /manualpeerlist:asia.pool.ntp.org /syncfromflags:manual /reliable:yes /update
Singapore
w32tm /config /manualpeerlist:ntp.x.znx.cc /syncfromflags:manual /reliable:yes /update
Stratum one servers
https://support.ntp.org/bin/view/Servers/StratumOneTimeServers
Stratum two servers
https://support.ntp.org/bin/view/Servers/StratumTwoTimeServers
NTP Pool Servers
https://support.ntp.org/bin/view/Servers/NTPPoolServers