I worked on a project that had a few spots where we compare a saved timestamp to the current time. During testing, the client would randomly change their device time a few days forward or backward and complain that things weren't working as expected. I had to explain to them multiple times that they were basically time traveling, and the program was actually handling it fairly well all things considered.

well thats the funny thing, it's technically not time travel, it's just time dilation if you squint hard enough. So technically, it doesn't matter.