Being arrested is still just the arbitrary choice of people. It's not real in the sense defined earlier. It is not like, say, needing to harvest food before winter sets in.
Look, I love Baudrillard as much as anyone, and we can talk about simulacra all day, but it's simply not germane. We're not talking about whether these restrictions are societal constructs but rather whether they are predictable, reasonable, and controllable.
The tax deadline is predictable. A two-month restriction from holidays is relatively reasonable. The deadline is not realistically controllable. (Your employer cannot eliminate tax filing.)
How is one of those more real? They are both actions that people undertake to accomplish an objective, but there is nothing tangible or factual about either, which appears to be your working definition.
What makes you think any are more real than any other? If you had taken the time to read the thread you would have learned that the whole idea of a fake deadline is nonsensical.
You had the idea that "the whole idea of a fake deadline is nonsensical". That could only have come to you because your idea of what a fake deadline is is wrong.[1] Because they exist, so the idea of them is not "nonsensical". HTH!
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[1]: So that's at least two ideas that you obviously have; putting the lie to your "I have no idea".