There’s not much proscribed and what is proscribed I agree with and do not engage in. But I’m assuming you meant to use another word besides proscribed.
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Ouch, you are correct, the use of proscribe was incorrect. Wildly incorrect at that. Oh for an edit button. And now it’s really hard to ask a somewhat snarky question after botching my word choice.
Change proscribe to prescribe. You can take it from there (or not).
Assuming you're genuinely curious what's observed is that which can be observed under the new covenant. For example, sacrifices are covered by the shed blood of Christ per the book of Hebrews.
If you're still curious there's more information at this link about these holy days.
Take care...