I have a Raspberry Pi. It has no RTC.
When it loses power, it has no idea how long it's been off until it checks the current time with NTP.
I installed ntpd on it, and am running it as a systemd service. That works fine.
I have software running on the Pi that does non-essential, time-based stuff. That means that if the current system time is accurate, it can do the task, but if the current system time may or may not be accurate, it can (and should) skip the task.
The way to know if the system clock is accurate, conceptually, seems simple - if the system has successfully used ntpd to update its time since it booted, the clock is accurate. Otherwise, assume the clock isn't accurate.
Is it possible to somehow get ntpd to tell me if it has successfully connected to the internet, retrieved the current time, and updated the system clock since last boot? I would rather not have my software try to parse ntpd's logs, if I can avoid it.