Forced To Sleep In The Afternoon . What To Do?

[drknow]

I am currently forced to sleep from either:

10am - 6pm (great amount of sleep for me of 8hrs )
12.30pm - 6.30pm Monday, Wed, Fri ONLY (slightly less sleep of 6hrs)

We are going into winter where I live so
sunrise is currently @ 7.15am
sunset is currently @ 7.40pm

I know this is not ideal but I am wondering what measures I can take to remain healthy.

Any ideas, research or articles that might be helpful to me in this situation would be greatly appreciated.

Thanks :)