So, SleepingOverhaul is a mod by CosmicDan which replaces Minecraft's default "snap-to-morning" sleep model by accelerating time whilst players are sleeping, allowing things to continue to process, grow, and progress as would happen in the real world.

I have a modpack that, (hopefully only temporarily) up until today, contained Quark, as it turned out to be the culprit for blocking SleepingOverhaul's functionality. Here's what happens when Quark and (heretofore SO) SO are un the same modpack: You go to sleep, and as would normally occur with SO, a little clock appears over your hotbar and Health/Hunger/Armor display. Time begins to accelerate, and after only a couple in-game minutes, (real-time, about a second) the snap-to-morning mechanic re-asserts itself, and instead of accelerating through the night as it should, it's immediately morning.

Okay. I hadn't gone through Quark's options, so I was unaware that was configurable. Thanks for the tip; I'd really love to have both, as Quark really adds some wonderful features and fixes.

That did the trick quite nicely. Thank you very kindly!