NP, problem here is that we parse a date against multiple pattern and if none of them match, we throw an exception. problem is to distinct a useful exception message from one parser to the others that are not, the parse index sadly does not help, because it “fails“ very early.
i will keep the ticket open, but remove the “regression” keyword, so it will not stop the Lucee 6.2.1 release (this is not a regression from 6.2.0 to 6.2.1 anyway)
We work on improve the performance of the parser anyway, maybe we can also improve this situation alongside.

That is interesting! I actually pulled that date from a test case that was failing. I will correct that date to a valid one. Sorry for making you run this one down.

in Lucee 6 we switched from the old SimpleDateFormat to the modern DateTimeFormatter that seem to be more percise, problem is your date "Mon, 31 Dec 2038 23:59:59 GMT" is invalid, this day is a Friday and not a Monday, so it should be "Fri, 31 Dec 2038 23:59:59 GMT", it took me far to long to find that out myself, only dumping some underlaying exceptions

i will see if we can expose the underlaying exception as caused by so it will be clearer, so you could say this was a bug in Lucee 5 that it did accept this invalid date.