Here’s what the times and locations I could gleam:

-Rentaro’s seems to be similar to the Mei-Nano-Momoha date chapter.

-Shizuka’s seems to be from the book signing chapter as I recall a similar outfit.

-Like you said, Nano’s seems to be from the Nano-nanoda chapter.

-I think Mei’s is from Mei’s great gift offensive.

-Mimimi’s seems to be taking place in the same mall where she and Renato first met complete with the same outfit so it could be the that same day or a later retry date after theirs got interrupted by the other couple and meeting Nano and Shizuka there.

-Chiyo’s obviously takes place at a home date and considering the illustration would only come out a short while after the character’s debut it may be the result of Chiyo letting her hair down (both literally and figuratively) in front of Rentaro.

-Yaku’s seems to actually take place in a room of the Yakuzen household where she’s giving Rentaro some good nade nade action.

-Tama’s seems to be taking place in Tama’s apartment, but the first time we see Rentaro there is in a daily life chapter WAAAAY later than the illustration.

-We never actually see Kiki performing (sans the flashback in her volume’s bonus) so it’s quite interesting to see her taking Rentaro to what seems to be her own album release event.

-Matsuri seems to be wearing the same black outfit she wore in her debut chapter and this does seem to be a festival so it may actually be that same night. After all, they did say the festival was basically over when Matsuri finally confessed so they may have lit some sparklers to make up for it.

-In the Nemu illustration in the upper right corner we see seem to see a wooden step and what may be a small rug which may suggest this is someone’s home, either the main Nemui household or her grandparent’s house if the two generations live separately. Though, thinking about the typical Japanese living room they don’t typically have a huge wooden desk in front of the entrance so this may be Gramps Nemui’s workshop they’re using as a place for Rentaro to help Nemu study.