For past 8 years I have been working on varying shift jobs. Initially I used to work night-shifts. That changed my sleep pattern entirely, so that it began to take effort to fall asleep early in the night. Now, things have settled down- I usually will work till morning hours 3-4 am and then go to sleep and wake up around 9.30-10 am. This gets me totally refreshed. Else, I need to doze off after lunch, sometime around 2 pm, for an hour or so. For a couple of days now, I am trying to get to bed early and to rise early - but even so I cannot go to bed before 12 midnight.