We talking to #1983 levels or lower

@Zaid K. Dahhaj do you know if there was an era with the "best" or most optimal lightbulbs for human health?

what about candlelight? Any rules of thumb? For us it cuts close to sleep, but try to reduce any light and use candlelight up to 30-60m before sleep

I nearly made a statement about candles, which I already make regular (but not yet consistent) use of at night. It's a difficult switch for many people to make because it requires regular material expense and forming new habits. I still encourage it, but I more strongly encourage people to spend time outside in the sun.

2500k is the sweet spot,4000 and above feels too industrial.

You can still get them, just look for 2500k, stay away from anything in the 4000k range and higher, they emit a lot of blues.