They say " it takes more than 24 hours for an egg to fully form (white and shell added), so a hen will lay an egg later and later each day." I've found this to be the case with mine. Eventually they skip a day.
It takes about 25 hours for an egg to be formed in a hen's body. So, each hen should lay about an hour later than she did the day before if she's a daily layer. If her latest rgg comes around sunset, she may skip a day, then start again early the following morning. @aart has a link to a fascinating graphic showing the development of the egg, perhaps she'll share it here.
Mine are all going through their first winter and while most went through a short winter break I think many of them have come back into lay, but some are still sporadic. It seems when most are going to lay they seem to do it all at the same time around 10am-2pm. Rarely do mine lay after about 4pm. I've seen up to 5 of my girls trying to lay at the same time, which is interesting seeing as they insist on only using 2 spots and would rather wait their turn than use another nest box. So there will be days when I hear a lot of squawking as they tell the one laying to hurry up.
I expect to see quite a few by 11am tomorrow seeing as I only got 5 instead of the usual 8-12 I've been getting.