The year of whose lord?

[Minimalist]

What exactly was it that Caesar Augustus decreed, according to Luke 2:1?

He decreed nothing, asshole. It's phony shit just like the rest of it.

As it so happens Augustus left a written record of the 3 times in his reign when he conducted a lustrum which was a count of Roman citizens and would have had nothing to do with a bunch of peasant poopers from Galilee which was part of the independent kingdom of Galilee and Petraea at the time.

Unfortunately, for you and your bullshit ( and there really is no point in reading the rest of what you wrote because your premise is fucked up) in the Res Gestae Divi Augustus http://classics.mit.edu/Augustus/deeds.html

and in my sixth consulate (28 B.C.E.) I made a census of the people with Marcus Agrippa as my colleague. I conducted a lustrum, after a forty-one year gap, in which lustrum were counted 4,063,000 heads of Roman citizens. Then again, with consular imperium I conducted a lustrum alone when Gaius Censorinus and Gaius Asinius were consuls (8 B.C.E.), in which lustrum were counted 4,233,000 heads of Roman citizens. And the third time, with consular imperium, I conducted a lustrum with my son Tiberius Caesar as colleague, when Sextus Pompeius and Sextus Appuleius were consuls (14 A.C.E.), in which lustrum were counted 4,937,000 of the heads of Roman citizens.

So nothing matches but again, it would hardly matter because what appears in Luke is nothing but horseshit.

What Josephus recounts is an assessment of the newly-formed prefecture of Judaea - nothing about "the whole world" which seems like typical xtian self-aggradisement for the so-called god. Wake up.