I suspect that the trigger is the shortening and lengthening of the daylight hrs. This is certainly true with my horses developing a winter hair coat. They will start to shed their winter hair around the last week of January! and by April they will generally have shed all their winter hair. Then in the first week of August they will start to shed out their summer hair and get their winter hair coat. By End of Oct they will have their full winter hair coat.This could well be true. The supposed '14 hours of daylight to lay' is not true for me, as we haven't had 14 hours of daylight for quite a while now (we are presently at 9.5 hours of daylight per day) and some of my girls are still laying, despite moulting. (And, yes, I know many say that they don't stop laying when molting..but I have 2 hens that molted hard and stopped laying, that have now 'come back online' and are laying 2 eggs a week....definite slow-down from their 4 eggs a week - but they are back to laying. My experience is they will keep laying like this except for a real deep cold snap, then they will stop (they are EE & and ISA, only my heavy Brahma and orps lay during a cold snap)
Also, young ones that didn't start laying in the fall for me did start laying in mid-to-late January, when the amount of daylight was similar to now...but on the increasing end. I've only had 'later hatch' ones once (plus this year...we will see what they do...a couple of the co-broody raised girls are really starting to pink up - @20 weeks now) so we will see when the first egg is.)
I do find that in the spring, the younger they are, the quicker they get their 'spring flush' lay on, usually early Feb. Older ones start increasing laying mid-to late Feb, and my 4+ year olds in March start increasing (or start again) laying.
This makes me think that I need to start keeping as detailed a record as possible. Since I have so many birds, I can't always tell who is laying what, but I can keep track of exactly how many eggs are laid a day. (I do count them daily from each group to mentally note the changes...but I presently only record how many doz. eggs are sold, and whether from the cooler or to specific people at work. Noting how many are chicken eggs & how many are duck eggs.)
I suspect that there will be some variation based on local clime and total daylight hours. Someone now living nearby used to live in Virginia, and she was absolutely shocked at how dramatically the laying dropped in the fall - she said previously, in VA, it was just a slow taper, and they didn't stop laying in the winter. Here, most of mine that are 2.5 or older stop for at least part of the winter....I do not know what breeds she had, but they were the same breeds as she got here, she said.
I noted that the chickens seemed to follow with the eggs, they started to slow down around mid August and now I am only getting about 2 eggs a day. I will be interested to see what happens around the end of January / beginning of February with eggs!