Terrible PEP, I hope it gets rejected. One-off flags like this are hacks that shouldn't be in stdlib. It simply stinks, in an area (time handling) where the stdlib does not really smell like roses already.

Dealing with time adjustments is the OS's job, not userland. If your job has to be scheduled exactly and cannot rely on the OS, and you refuse to deal with UTC, it's your own damn fault and you can always just use a long-running process with timers.