Three theme answers suggest periods that would be difficult to schedule, without the fourth theme answer, CALENDARREFORM. I like EIGHTDAYSAWEEK and AMONTHOFSUNDAYS, but while I see how LASTWEEKTONIGHT fits the theme, I think it's a little OFF compared to the other two.
I've always enjoyed the fact that civil rights pioneer W.E.B. Du Bois' initials spell WEB (there's a W.E.B. Du Bois Research Institute where I work), so I'm positively inclined toward 1A, but the end result is still ATAD humdrum, so I give it a B.
My favorite clue in today's puzzle is 8A. Rant (TIRADE), which I like much better than 19A. Ranting (RAVING) for some reason.
I was surprised to see 28D. Google __ Viewer (tool for charting word frequency over time) (NGRAM) in the puzzle at all, never mind on a Monday. Not that it was difficult fill, but I didn't know people knew about it, or, rather, that the constructors would expect solvers to know about it. Have any of this blog's esteemed readers heard of it and/or used it?
OWIE (55D. Little injury, in baby talk) makes an appearance for the third day in a row today, which makes me wonder, what is the longest streak for a puzzle answer? I have a lot of questions today.
The grid includes a year's supply of abbreviations, with a prominent band across the middle starting at 36A (ETC, ATL, ISO, ROO). Maybe it's celebrate STENOS day??