potmo We all have the same 24-hour twofer period each week - for clarity I'll call it 12:00:01am Hawaii time Sunday through 11:59:59pm that night Hawaii time.
For you on the North American mainland, most of which has daylight saving time, that will vary in your local time by an hour depending on time of year - for you right now, I think that's 5am Sunday to 5am Monday?
So unless you're going to get up before 5am on Monday, your (local time) twofer period is effectively Sunday. (Though of course you also have part of Saturday, after the theme is announced, to record, though you can't post it on the thread until Sunday.)
(But you might choose to record one on Saturday, post it Sunday morning, and call it a “Saturday twofer”, and record and post another on Sunday and call it a “Sunday twofer”. And you might still get up early Monday and post a “Monday twofer”, if you were so inclined. You actually have access to three separate days between the usual announcement time and the end of the 24-hour twofer period, if you’re obsessive enough to care about such things. 😆)
For me though (no DST here), the twofer period is always 8pm Sunday to 8pm Monday. Most weeks, the theme is posted early Sunday morning my time.
So I can record what I call a "Sunday twofer" any time Sunday, and usually if I do that, I'll post it right at 8pm Sunday on the thread, which is the start time of the new Season. (I actually have an alarm to remind me, which is why I'm often first to post for a new Season. It's a lot easier to do that here in Australia at 8pm, than in Kansas at 5am (or 4am in the wintertime!)
For me the “old Season” then ends at 8pm Monday, so now I have all day Monday to make a “Monday twofer” if I want to. (I am well aware that when I make and post my Monday twofer, it is still Sunday for most of you. But here, it is Monday, usually Monday afternoon or evening.)
Does that make it any clearer?
For reference, Hawaii time is GMT-10 (10 hours behind Greenwich Mean Time), CDT (Central Daylight Time, which I believe you’re in now) is GMT-5, CST (your time in winter) is GMT-6, and Brisbane (where I am) is GMT+10 (10 hours ahead of GMT) - we’re near the leading edge of the day, 20 hours ahead of Hawaii.
(PS, if you start posting Saturday twofers, I may be slightly envious, because those are never available to me. 😆 Especially if you follow one up with a Sunday twofer and a Monday twofer, because that is not possible for me!)