It’s neat but I don’t think fixes these issues because they have to integrate with live systems. You can lie about system time in tests by making everything else have the same time.

That doesn’t apply if I need to hit gmail.com and can’t login because my system time is a week behind and the JWT says it isn’t valid for another week.

Even if you make everything else accept the time, timestamps will be screwed. Like in a fake gmail service that accepts mocked times, what do you use for timestamps on emails?