Maintenance and DB Backup occur based on time too... I'm sure Murphy's Law dictates that within 2 weeks of going NTP'less, those events will occur at whatever the worst possible time is. 
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It's mostly for security anyways would probably be better if it did drift since people tend to break into vacant property between 2 and 4 am. And maintenance seems to happen around 2:15am.
Would it be a bad assumption that you also take a laptop when in your RV? With that you could connect the hub directly to it by using a hard-coded IP address and update the hub's time via the laptop browser. Without occasionally connecting your laptop to WiFi and getting its clock synced they could both be off by some nominal amount of time but who cares?
And how much can the hub's clock drift anyway? It would need setting on each power-up but I can't imagine it goes off the rails in a day or three.
I left out something very important. I won't have a router in my trailer so there will be no WiFi network. My laptop does have an ethernet connection for connecting to the hub. When camping outside of RV parks (boondocking) there is rarely WiFi. Even in RV parks WiFi is spotty.
Also I'll only be using it when I'm traveling and away from the trailer. Not when I'm present or the trailer is in storage.
If you have cell service your phone can be used in several ways to connect anything to the Internet.
You might enjoy a read of this Topic...
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You can plug an RJ45 cable directly from laptop to hub. You just need to manually assign IP addresses to both, putting them on the same network. We use to need a cross over cable to do this, now every NIC can detect a direct connect and do the cross over for you. Connect, open browser, punch in hub IP address, open settings, click hub details, and update time from browser time.
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True. My truck is also capable of being a WiFi hotspot. However I want to know if I can do this totally without an internet connection or WiFi.
How long ago? My laptop is several years old.
[quote="[PROJECT] Smart RV (with photos) Lounge, post:1, topic:10542"]
Warning... This is a long post! As much as I like playing around with technology,
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Thanks. Interesting thread which I'm still reading.
I think it doesn't matter as long as one end is new enough to do the auto-negotiation.
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15 years or more. You should be ok unless it's running Windows 98 or ME.
Maybe something like this?? An ntp time server using satellites.
https://www.ebay.com/i/362768894932
I have NO idea how well these work.. maybe also try and find a WWVB to NTP device but I think those are rather more expensive.
Also maybe this for the Raspberry PI:
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You could probably do it with an Arduino, given the very light load.
I have not tried these.. just pointing out the idea isn't new.
https://www.geekstips.com/arduino-time-sync-ntp-server-esp8266-udp/
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Has anyone taken the time to see what a typical clock drift might be? I would guess the processor has some counter that might be off a bit (assuming no 32768 crystal) but I would think it is pretty stable.
I think the bigger issue will be the mobility of the hub. You'll need to keep updating the location to keep sunset/sunrise close to accurate. The clock will drift by seconds, the location may change by time zones.
About 1 year ago I was running a hub without internet and the time would reset to the Date and time the hubs firmware was completed, so it might go back to midnight a month and two days ago during the DB maintenance. It was terrible back then and the NTP driver wasn't available yet so I had to run an AtJob from a windows machine to set the hubs time every hour to make sure it was correct. Once the NTP option was available I changed to using that and shortly after that they supposedly made some changes to try to keep it from changing the date but I never bothered to turn off the NTP driver long enough to see how much it improved.
But doesn't the NTP driver require the internet? Or am I missing something.
It requires an NTP server.. not necessarily an internet connected one.
Arduino + GPS Allows you to make a non-internet NTP server. There are Topics that include this here on the Community.
And of course you can always buy your own cesium clock. 
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