A while back, there was a discussion between a few of us. I can't find it to refresh my memory on the whole context, but it was something to do with the day Yeshua was resurrected. I quoted a verse that included "first of the weeks" yes, "s" included. I dont remember the semantics point I believe Chris Deweese was trying to make out of it, but I found another place it is used for the dsy of pentecost:

Joh 20:19 LSV It being, therefore, evening, on that day, the first day of the weeks, and the doors having been shut where the disciples were assembled through fear of the Jews, Jesus came and stood in the midst, and says to them, “Peace to you”;

If someone could direct me to the conversation, I'd like to review it. Thank you!