I don't do anything like that. I just rely on the device's clock. Again, for my simple needs (to-do list), it works fine. It could be a problem if you have a device with the wrong time, but even then it would require a single user to be making lots of changes on the same property of the same object within a very small window of time, which for a to-do app is very, very unlikely. I didn't want to solve problems I didn't have.
Sounds like you created a simple, pragmatic solution for your use case. Which is exactly what you should do. But the method probably can't be applied to mission critical systems without changes.
My solution was designed for a very narrow use case where there is one user and multiple devices. The main reason I designed it because I did not want to stand up a cloud service for storing user info. I wanted to offload that responsibility to a file sharing system like Dropbox or OneDrive. It's not meant for anything beyond a very simple use case.
