When the order was placed, the ship date was Monday, Sept 18. On Sunday the 17th, I was concerned that we might not get the order ready in time to ship the next day. So I went in to explain this to the customer and update the ship date to that Tuesday just in case we needed the extra day. I wrote the note, then hit submit. I completely forgot to change the date. Then I noticed that in forgetting to choose a date, it had automatically changed to the day I was sending the message - Sunday the 17th.
I thought, well now we have to work a bit harder to get it out by the 18th like it was supposed to go because surely it wouldn't really think the 17th was a ship date being that it is a Sunday. We did successfully ship it on the Monday the 18th. But then I noticed that there was a change to my ongoing Star Seller stats, and found that this order indeed had been marked as shipped late!
I contacted Support, and they assured me that it sometimes takes 24-48 hours for the data to update. No problem, that made sense, so I waited. Nothing changed, and now unfortunately it has affected the stats for my Star Seller status to the point that I do not qualify. If that one order were not included, then I would qualify. I reached out to Support again today, and although they understood that things cannot ship on a Sunday, and that it is frowned upon to create labels that won't actually ship on the day they are created, they have no power to change the Star Seller data. I understand that. However, shouldn't there be someone who can? How can a ship date be for a Sunday?
Etsy will assume that you ship ALL days unless you indicate otherwise. Saturdays and Sundays do count as shipping days.
And because you (accidentally, but the bots don't know that) indicated you would ship on Sunday, you shipped late.
Etsy has said they will not adjust the sats retroactively. It sucks, but that's the way it is.
Better luck next time.