I say that because, IIUC (and that's a real question), quantum mechanics treats the time dimension as symmetrical, which contradicts observation, at least to th

I say that because, IIUC (and that's a real question), quantum mechanics treats the time dimension as symmetrical, which contradicts observation, at least to this point. As far as I'm aware, the weak force is known (and experimentally demonstrated) to break time-reversal symmetry. It's only combined Charge-Parity-Time symmetry that QM maintains. (This still does not explain how a macro arrow of time arises, though)