I find that 8 hours of sleep is absolutely not enough. I sleep at least 9 on good days, 10-11 on pre-flare days, and 12-14 on flare days. These amounts of sleep are the only way that I function. I do find that sometimes sleep is hard because of pain and fatigue so I'm thankful for a muscle relaxer, rain noises on my sleep app, a weighted blanket, epsom salt bath and/or melatonin. Usually the relaxer plus one of those others will do me in, but you've got to find what works for you.
I also have to appropriately "wear" myself out some days by using my standing desk or going for a slow and easy walk/ Tai Chi or even just really exhausting my brain and I make sure to NEVER drink caffeine after 1 pm. I found these things work for me after experimenting with sleep rituals and logging on what I was eating and moving effected my body.
As for going from night to day...I was a late nighter when I was an improv performer but my job didn't demand much from me so I was kind of a ghost during the day. Recently I had to switch to fully functioning days and to help with the being sleepy thing I make sure I honor my sleep needs and I really lean in to my sleep ritual. I start going to bed about 2 hours before I'm actually wanting to sleep.
I do soothing things, turn off the TV and phone, play soft music, take a bath, drink some herbal tea and by the time I need to sleep I'm ready to sleep. I also know I need plenty of time to get up so I skip the morning shower and use that time to warm up my gelled joints with stretches and movements in the bed...on hard days I might even use a heating pad on them.
But if you can move your schedule to fit your sleep needs do it! I know plenty of night owls and you just gotta work when you can work and sleep when you can sleep!