Three of my labours started in the early morning (5-6 am). One started in the early evening.
My 2nd labour was with a persistent posterior baby. With him I had 2-3 days of pre-labour--very strong but irregular B-H which interrupted sleep. Then the day of, I had more symptoms & regular contractions began at about 10 pm. When I got to the birth centre a couple of hours later I was 7cm! I was so pleased because it was a first VBAC and then I knew I'd have the baby that night.