"lights out" (screen lights count too)

Perhaps just say "time to get ready for bed"?

Eh, time to go to sleep or get ready for bed? I mean same concept, different words.

"Eight hours before time to get up"?

At my house we called it "Quit stalling and get your ass in bed".

My wife and I (late 40's, with no kids) refer to it as sleepy time in our house, but that probably isn't any better than bedtime. 😆

Time for non-eternal rest

Subconcious Brain Adventure Time

I asked ChatGPT but I don't like its suggestions:

It's great that you're open to finding a suitable alternative to calling it "bedtime" for your niece. Here are a few suggestions you can consider:

1. "Restful Time": This term emphasizes the importance of getting enough rest while still sounding more mature than "bedtime."
2. "Dream Hour": This phrase adds a touch of imagination and excitement to the idea of going to bed, making it a more appealing concept for your niece.
3. "Sleepy Time": This option retains the focus on sleep but removes the "baby-ish" connotation, allowing your niece to associate it with relaxation and getting ready for a good night's sleep.
4. "Night Routine": This phrase focuses on establishing a regular evening routine, which includes winding down and preparing for sleep.
5. "Quiet Time": This term emphasizes the need for a calm and peaceful atmosphere before going to bed, which can be appealing to your niece. It would be helpful to involve your niece in the decision-making process by explaining why you're looking for an alternative term and asking her for any ideas she might have. By involving her in the discussion, you can find a term that both of you are comfortable with.

Tell her it's time to hit the hay.

TEMPORARY COMATOSE STATE WITH POSSIBLE STRONG HALLUCINATIONS AND SUBSEQUENT AMNESIA

Well, her problem is probably just the idea that she has a bedtime rather than the terms used.

My solution would be to have some sort of loud speaker telling everyone something along the lines of "NOW IS THE TIME OF SLEEPING". If you have some kind of home assistant thing you can probably set that up. That could be paired with warning count downs and automatic dimming of lights.

I actually have a routine on Alexa that turns off lights and starts dimming others for me.

Time to hit the sack, hit the hay, or lights out.

"Let's call it a night"

fin like the movies, imagine it like your day is the end of a episode in your life

Time to get some sleep so you have more energy to do things tomorrow!