VMware vCenter Server 6.x
VMware vCenter Server 7.x
Configure using the vCenter Server Appliance Web Console (VAMI):
Log into the vCenter VAMI as root:
https://<vCenter_IP>:5480
Select Time.
Navigate to Time Synchronization.
Click Edit.
Under Mode, select NTP.
Type in the NTP server(s) on Time servers.
Click SAVE