Triangulation Vibration Sensor Impact Detection Position
You don't need a timestamp, because the triangulation works on difference of time, so the absolute RTC time has no significance and adds unecessary burden to the MCU. You have to start recodrding with deterministic time (aka cyclic interrupt)in RAM all channels in a circular buffer, when you detect the impact you end the recordings.
Then I would use a cross corelation between each dataset to determine the delay, A vs B, B vs C, A vs C (A,B,C are signals), te cross corelation will give you the rate of similarity between each signal, at its peak value you have the most probable delay between towo signals, then all you have to do is triangulation math.