Thanks, I do suspect I have delayed phase sleep disorder. It's good to know I'm not alone. Do you have any coping strategies?
My coping strategy is 'modafinil to keep me from not being a zombie when particularly sleep deprived', and 'zopiclone for if I have been up longer than I should and it's early enough to push me back into normal sleep pattern'. But of course I'm very wary about doing that more than twice in a row, so it's never enough to establish 'normality'.