There is increased interest in Simulation federation, as evidenced by the new Accellera standards working group on the topic. One key aspect is how time should be synchronised. Meantime QEMU \cite{bellard2005qemu} (a well known open source emulator) is also changing the way so called {\bf ``icount''} (instruction count) mode works, allowing external mechanisms to both interrogate the icount on a per CPU basis, and adding, for the first time, an ability to control QEMU's time. Finally, the SystemC community has been interested in "parallel" SystemC for some time (e.g. \cite{rainers-2022}),  this paper introduces new structures in SystemC \cite{SystemC} which will be proposed for SystemC 4.0, and with which we test some of the time synchronisation concepts.

The main goal of this paper is to introduce a single "unified" API for synchronising time between different simulators. It will be tested between SystemC parallel threads, SystemC and QEMU and between SystemC processes using Zenoh \cite{zenohZenohFlow060rc, ZenohConsistency}.

It is time to talk about time.