On Arch Linux running as a guest OS on VMWare Fusion, I noticed the system time of Arch falls behind when I sleep the host OS and never gets back in sync. It appears systemd-timesyncd is loaded but inactive.
[root@arch1 ~]# systemctl status systemd-timesyncd * systemd-timesyncd.service - Network Time Synchronization Loaded: loaded (/usr/lib/systemd/system/systemd-timesyncd.service; enabled) Active: inactive (dead) since Tue 2014-09-30 11:04:42 PDT; 3min 7s ago start condition failed at Tue 2014-09-30 11:04:42 PDT; 3min 7s ago ConditionVirtualization=no was not met Docs: man:systemd-timesyncd.service(8) Main PID: 17582 (code=exited, status=0/SUCCESS) Status: "Idle."
Update: The answers below explain how to get the systemd-timesyncd.service running under a VM, but it turns out that doesn't solve the time sync problem (which is probably why systemd-timesyncd is disabled under VMs). The Arch wiki page Installing Arch Linux in VMWare explains how to perform Time Synchronization between guest and host OS.