I don't know when I slept.
I slept the whole time after that.
I was going to bed.
When I realized it, I was sleeping.
I thought that you were sleeping.
I took a doze after coming home.
In those days I went to bed earlier.
In those days, I went to bed earlier.
Before going to bed, I went round to see that the doors were fastened.
Before I realized it, I was sleeping.
Even though the alarm clock went off, I didn't wake up.