Like most anything, there are methods and designs (best practices) which if followed, will prevent you from falling into pitfalls like that. It’s generally only a problem if you design things to use time and not account for it. And as for the time changing while an operation is currently occurring, this again, is what transactions and other “atomic” type of operations are designed to account for. There is a lot about computer science where you need to make sure the sand you’re standing on isn’t shifting when you’re on it.