I had to support an IoT device once that lacked an RTC. That was actually the easier hardware platform, because it either had good NTP sync or it didn't reach

I had to support an IoT device once that lacked an RTC. That was actually the easier hardware platform, because it either had good NTP sync or it didn't reach our C&C servers. The difficult one was the platform that had an RTC. Those would slooowly drift out of sync if NTP was broken. Slowly and silently.