We both understand your concern and we have the same priorities. OpenSprinkler should and will work without an Internet connection. Everything the Internet and our cloud server provide is optional. Let me go through the data and clarify how it’s used and what happens if the controller can’t update.
Time (NTP): The controller has a real time clock which will keep time if the NTP server cannot be reached and only minimal drifting will occur with this alone.
Time (timezone): The timezone is set once by the cloud per location and is not modified after that. The cloud resolves the locations timezone however if you empty the location field the app will let you change the timezone manually. Furthermore, the cloud does resolve the state of daylights saving time so this will not change if the cloud cannot be reached.
Sunset/Sunrise: This will update daily the values from the cloud however if they cannot be updated, the previous values are used.
Weather Adjustment: If the cloud cannot be reached, the water level will stay at it’s current value otherwise it will be adjusted based on the method (Zimmerman) and the conditions. Of course the water level can also be manually adjusted.
As you can see nothing is critical to the cloud but it does offer extras. As you have noticed, the controller forgoes network checks during running programs to ensure no interruption is incurred. I hope this helps clarify the use of cloud and also helps reassure you we have the same philosophy in mind with regard to working regardless of Internet connection, etc.