The *zwavejs2mqtt* and *zigbee2mqtt* services need to wait until the
system clock is fully synchronized before starting. If the system clock
is wrong, they may fail to validate the MQTT server certificate.
The *time-sync.target* unit is not started until after services that
sync the clock, e.g. using NTP. Notably, the *chrony-wait.service* unit
delays *time-sync.target* until `chrony waitsync` returns.
Dustin C. Hatch
465aa4d78e