Standard paleo/primal advice is roughly alone the lines of things like when it starts to get dark start to wind down for bed, sleeping in a completely dark room.
I'm not going to argue with the completely dark room bit.
But I do have a problem with the whole when it starts to get dark bit. I live in the UK. I live in the south of England actually so our problem isn't as bad as the likes of Scotland. The difference is noticeable actually. A friend of mine lives near London and regularly travels back up to Scotland. When we spoke last night we talked about light levels and the difference it makes just with that short distance.
According to google Glasgow is about 56 degree N. Where I live is about 50/51 degrees N. Contrast that to 34 for LA. 41 for NY.
What this means is that at this time of year, the height of summer, well I'm sat here about ten past nine and there's still plenty of light for reading outside. In the middle of the winter "dark" is from about mid-afternoon and doesn't clear until a fair way into the morning either!
Summer is actually with us here in the UK at the moment. Which means a couple of weeks of muggy sunny weather. Sunshine is lush but the mugginess is horrible. We don't really do air-con here in the UK because, well, it would probably only get used a couple of weeks a year. So at the moment we're struggling with stuffy over-warm houses that make it difficult to sleep. I heard on the radio this week someone saying that they got so hot they decided to sleep in a tent in the garden. I have considered it myself this week to be honest but it's a bit difficult to sleep in complete darkness when it gets light by half 4. I don't own proper blackout curtains so I'm using blankets over the normal curtains. I've been sleeping badly.
If, for the first time in years, we get a summer that lasts more than a couple of weeks I might try and organise myself so that I get some sleep in when I get home in the afternoon and then do stuff like dog walking and cooking in the middle of the night before getting some more sleep. Because I've been waking up in the middle of the night anyway.