Since the "Day of the Lord" refers to a group of events (Jesus's return, the judgment of the nations, and the rewarding of the righteous), I think we're remiss to look for a specific day and hour of a particular event.

The text doesn't actually say "Day of Rebellion," even though I used that phrase colloquially. The text reads, "Don't let anyone beguile (deceive; seduce) you in any way, because it (the Day of the Lord) will not come until first [comes] the apostasy (the revolt; the falling away)." You can readily see that it's not necessarily talking about a singular event that happens at a specific hour, though that is always possible. It could mean that there will be a growing apostasy preparing the way for Jesus's coming, and there might even be a huge event of rebellion right at the end. There will obviously be a large movement against the truth. It makes sense to envision it as a period of time rather than only a specific moment in history.

This is a great answer, thank you for all the detail.

Is "The Day of Rebellion" the day this group of followers truly turns against God, then?

"Lawlessness" is the Greek word ἀνομίας. νομίας means "law," and the prefix "a" means "without law," the same way we use amoral or asymptomatic. Paul puts the word in parallel with "the son of perdition" ("the man doomed to destruction" at the end of v. 3), and he describes this "man of lawlessness" in vv. 4-10:

[list][*] He sets himself up as God, presumably seeing himself as the law-giver and the arbiter of right and wrong.
[*] He opposes everything about the true God
[*] He will be much more like Satan than God (v. 9), though he will set himself up as God (v. 4)
[*] He is, for the time being, working under the radar, but he will eventually be revealed (v. 7).
[*] He will be able to do miracles to wow the crowds and win them over (v. 9). The point will be to deceive (v. 10), and therefore "deception" is part of what we are to understand by "lawlessness."[/list]

The section is generally thought to refer to the End Times, and this "Man of Lawlessness" is thought in some circles to be the Antichrist.

> Are there examples?

The text seems to be referring to a specific individual who will come at a particular time in history. While there have been plenty of religious deceivers through the millennia, this section is prophetically about the day of rebellion (v. 3) preceding the Day of the Lord (v. 2)

2 Thessalonians 2:3-10 - How is lawlessness defined here? Are there examples?