A 23-28 hour cycle but a need for 14 hours of daylight, hence the increase in egg production in spring and summer (and commercial enterprises using artificial light to keep the birds laying, wearing their poor bodies out even quicker). Plus the effect of the increase / reduction in daylight, so even with more daylight in August they can lay less than late winter / early spring.
I’ve also found that during weeks when I tend to the chickens at more or less the same time every day, they tend to lay very predictably and roughly the same number of eggs by the same time. Other times, when life takes over and the daily visit to the chicken coop is more random, the egg laying seems all over the place and I either think of them as ‘way to go, girls’ or ‘slackers’. I like to think they prefer routine but really it was just me who needed a routine
And then there’s the impact of... (drumrolll) General Confusion In The Land Of Feathers
I’ve had chickens moult in February instead of September / October, going broody for Christmas, and drastically reduce laying for a week or so in May / June (looking back at it that might have been the weather as we have no predator attacks or anything to upset their little minds and hence bodies). Oh, and once there was red mite in February and it wasn’t even mild! So I now treat the coops year round with DE rather than just regular checking.
Nature does funny things