If you use NTP for syncing your time, then choose pool.ntp.org as your time server:
The pool.ntp.org project is a big virtual cluster of timeservers providing reliable easy to use NTP service for millions of clients.
I use it for instance to synchronize the time on my ESXi servers.
Note: when you run Windows VMs as ESXi guests; let ESXi time-sync them through the VMware tools, and disable Windows’ own time syncing. I didn’t disable it, and my Windows VMs were consistently off by over 30 minutes.