Is it still considered 6 months for a stale dated check?

Yes. Although all that really means is that a bank doesn't have to accept it. But it's still valid and most banks would probably take it. Assuming we're not talking about a bank cashier's check.

Also, the paying bank could send it back, but I don't know that anyone would catch that unless it's a really large dollar amount.

Tellers shouldn't knowingly accept a check over 6 months old for deposit, especially if drawn on another bank, because they can't know whether the paying bank will honor it. While it's true that most checks aren't checked for dates, when the dollar amounts get larger, banks tend to take a look at such issues.

According to Article 4-404 of the Uniform Commercial Code, a bank is not obligated to pay a check out of a customer's account when that check is more than six months old based on the date written on the check. Although banks are not obligated to pay a check, they are permitted to do so.

Can someone tell me what happens in January when all checks are dated for the year before, LOL.

Do all of those checks get unpaid, or is there some underlying assumption that it was written incorrectly?

And if that's the case, how does that work?

Honestly, most checks are not checked for date, and haven't been for years. It's just impractical with the numbers of checks processed at such high speeds. Banks may check the date on checks that are called to their attention for other reasons (overdrafts, flagged accounts, larger amounts, etc.).

Under the Uniform Commercial Codes of all states, a bank no longer has to return unpaid a check that is (or appears to be) more than six months old. They can pay those checks if they do so in good faith.

It's been many years since the changes to the UCC that allow banks to consider such checks properly payable.