Two months ago, you entered D pre-check and ended up in the D area (the way its been since P-C started). A month ago at 8 pm P-C wasn't open. Two weeks ago the "new arrangement" was in place: after the agent checked your id and P-C status from bp, you walked through a passageway (right-most end), which ended in C area; the "new P-C conveyor belts and metal detectors are HERE.
It must have started in the last two months(?)