I think that we can rid of requiring an external RTC with a battery backup.
The case where we need the RTC is to timestamp data which is collected between poweron and getting the proper time from the server.
What I'm thinking is that when we poweron, we can set the RTC to some fake time. Then when we log the samples locally we log them with the fake time.
Once we get connected to the server, we can get the realtime from the server and we can then correct the samples as they get uploaded to the server.
What this doesn't cover is the scenario where the device gets turned on, collects from samples while not connected to the net, and then gets powered off.
So the question is, is it important to have the RTC or not?