My time: 20:11, five minutes faster than average.
Theme: "It All Adds Up." In five places, where a Down clue intersects with an Across clue is indicated by circled letters that make (rather uneven, except in the middle) plus signs. Both these Down and Across answers contain the same letter strings which read as written-out digits (but don't represent numbers in their original form). The trick is that these letter strings are replaced with other letter strings that represent different digits, addends of the original letter string. That is, if you add the numbers written out in the Across and Down circled squares together, they add up to the original letter string.
You're confused, understandably. Here's the first example I cracked. The show "Days of our Lives" ("whose iconic hourglass is in the Smithsonian collection") contain the letter string F-OUR, or four. But because it crosses a Down whose similar letter string reads out four, those letters are replaced with TWO. Add both Across and Down circled letters — TWO and TWO — to read the answer as their sum, four. So it's in the puzzle as DAYS O(TWO) LIVES and should be read as DAYS O[f Our] LIVES.
The crossing Down clue is "1943 Pulitzer Prize winning Thornton Wilder play, with The" which is "The Skin of Our Teeth," appearing as SKIN O(TWO) TEETH, to be read as SKIN O[f Our] TEETH.
Another example. "Bygone office group" is steno pool. But it appears as S(ONE)O POOL, to be read as S[ten]O POOL because it crosses with (NINE)DED BAR, which is read as [ten]DED BAR ("made the rounds?"). Why? NINE plus ONE is ten, so the circled letters are read as ten.
In the last such clue pair, "neither gains nor loses" is BREAK(ZERO), to be read as BREAK[s even]. The crossing Down clue keeps its letter string seven in PRESS EVENT. That's because SEVEN and ZERO make seven, which is the original letter string for both phrases.
I hope that's all clear. It took me a few minutes to figure out.
I have never heard the term SUN TRAP to refer to a sheltered balcony that gets lots of natural light.
The Council of TRENT was held between 1545 and 1563 in Trent (or Trento, in northern Italy). It was the 19th ecumenical council of the Catholic Church, prompted by the Protestant Reformation. It has been described as the embodiment of the Counter-Reformation. Basically it drew up a list of purported heresies and condemned them.
Con MOTO means with animation, or in a spirited manner, in music.
I guessed that EDEN was the name of the "town near Buffalo that sounds like paradise," but couldn't be sure without crossfill. It is in Erie County.
I've heard of Thai BAHT but not the hundredth-part coin, the satang.
We've all heard of the sitcom "F TROOP" but not that it took place at Fort Courage. It was set from 1865 to 1867 or so.
ZAC Posen is an American clothes designer about whom nothing interesting is known.
ETA represented as H came up on January 16, 2018.
"Longtime CBS News correspondent" LARA / LOGAN last appeared on November 1, 2017.
I remembered OLGA, the eldest of Chekhov's "Three Sisters," last seen on September 19!
However, I forgot country singer K.T. OSLIN, from August 31, 2018 (when I also forgot her).
"INSECURE," the TV show starring Issa Rae, came up on July 3, 2018, with the star as the answer, natch.
Clever clues: "Don's partner in the underworld" is CAPO. "Melting point?" is ICICLE. "Pieces of gangs" is GATS. "Wanders around the head of a line?" is TSA. "Something that's helpful in a dash?" is GPS.
Holy TOLEDO (and Holy SEE)! That's a lot of old stuff, not much new stuff, and a pretty complicated theme! I'm exhausted. And that's THE LAS(ONE)RD, or rather, with an extra ONE added in, THE LAS[t wo]RD.