This is my first backyard flock and I am learning a lot about chicken behavior not only by direct interactions but through surveillance cameras in the coop and around the run. Respected references state that most will lay early in the morning. But my 6 gals never got the message. They lay as early as daybreak and as late as sundown. Each has a pattern of laying a little later each day until a late egg, then skip the next day, and the following day lay very early, and so on. The biggest surprise was a sundown egg laid while the others were already on the roosts!
You and you're observations are right and the respected references are wrong - sort of. It takes over 25 hours for an egg follicle to become an egg after being released from the ovary. The next follicle won't be released till after the developed egg is laid. Depending on the breed and individual, the lag time can vary dramatically. The future egg spends about 15 minutes in the infundibulum where it is fertilized if sperm is present, 3 hours in the magnum, an hour in the isthmus and 21 hours in the shell gland. The last time I checked, a day is 24 hours. So if you picture a 24 hour clock and a hen in a laying cycle. Lets say the first egg is set to be laid at dawn. The next day, the egg will be at least an hour later. That pattern continues just like you observed until the last comes at roost time. The next day, there won't be an egg. But what happens next is why most people think the eggs all come in the morning. Imagine that dusk is at 6 PM, lets go back to the 24 hour clock. The egg that would have come at 7 PM will be held over till dawn the following morning. The cycle continues but since they don't lay at night, every egg that would have come at all hours of the night will come at dawn. Depending on how productive the hen is, that could be six to twelve days in a row with all eggs coming at dawn and then an hour or 2 later every day starting the whole cycle over. So that's 8 to 18 days in a row with eggs coming in the morning and only 3-7 days with the eggs coming in the afternoon/evening. It SEEMS like all the eggs come in the morning, because most of them do but not for the reason some may think. It surely isn't because they choose to lay a certain time of day.