D5 has had multiple theories thrown around. The date one does fit with all the drops with that on them. I do not recall it ever being settled so here is my two cents on it. If younuse that mode of thinking then the rest of them falls right in.

2549 drop GHW Bush funeral services mentioned. It was on Dec 5, 2018 at the Washington National Cathedral.

4229 drop… D5 next to date on letter on, for an example and another mention with Dec 5th

2494 drop… has [D]ec 5 with D5 below it

2537 drop… "odds of a state funeral on D5?"

So the other drops mentioning D5 are Dec 5th