#1 was born just before 5pm, in March, so at dusk
#2 was born at 3am.
But I went into labor with both at almost exactly the same time - 4 or 5 in the morning. With #1 I labored pretty steadily, contractions staying constantly spaced, until transition and the birth.
However, with #2, when I got up and said "aha, I'm in labor!" labor dropped off dramatically. I had something important to do, and then I had to get my support person for #1 over to watch him. It wasn't until all the i's were dotted and t's were crossed that my body let go and went back into labor. Once it did, it progressed very quickly.
I'd be interested in seeing when people's labor started, as compared to when it ended...