systemd-time-wait-sync.service, systemd-time-wait-sync - Wait until kernel time is synchronized
systemd-time-wait-sync is a system service that delays the start of units that are ordered after time-sync.target (see systemd.special(7) for details) until the system time has been synchronized with an accurate remote reference time source by systemd-timesyncd.service.
systemd-timesyncd.service notifies systemd-time-wait-sync about successful synchronization. systemd-time-wait-sync also tries to detect when the kernel marks the system clock as synchronized, but this detection is not reliable and is intended only as a fallback for compatibility with alternative NTP services that can be used to synchronize time (e.g., ntpd, chronyd).
Added in version 239.