> Sleeping after sunrise counts for zero - it is useless.

I don't know about some people, but for me this is practically the silliest thing I've ever heard.

I need 8 hrs of sleep period, and the time of day has zero effect on my alertness. It can be 9pm-5am or 3am-12pm, it's exactly the same.

But if I get only 6 hrs of sleep? I'm miserable.

I can't even begin to imagine where the idea that the hour of the day matters would have come from.

And just think of nighttime workers. Obviously their daytime sleep counts...