Hybrid Time Physics

I accept that McTaggart's A-series and B-series are not inter-reducible and that both are needed for a complete temporal description of a physical system. I consider the Wigner's Friend thought experiment. The A-series are associated with each (quantum) system, and relativity is associated with the B-series. I consider temporal evolution through this 'hybrid' time. We may define the rate of temporal flow as 1 B-series second per A-series second.