Bit of an old reference for the day but one i must admit i have forgotten previously, when using a windows domain controller time source for your ESXi infrastructure you may notice that with the default settings you find that it wont synchronize.

Thankfully VMware have a workaround that requires a couple of changes on the ESXi hosts to change the NTP client settings. Instructions are even provided on how to configure you domain controllers w32time service to point to one of the many internet NTP services so you always have good/reliable time source configured.


For the ESXi client NTP changes heres the article reference