Depends on light cycles too. My EE started laying in the first week of January and every egg has been full size, large to extra large and misses only one or two days per month.
I don't know her actual age as she was a stray, but I've read that under natural light cycles chicks should be hatched in late April through early July so they mature under short and shrinking fall/winter days. The reason being that it allows them to get older and physically more mature before laying, while winter/early spring hatched chicks mature during the long days which stimulates earlier laying.(before they are fully grown)
There's a reason why the more wild breed seasonal layers don't start laying until about march. (with hatching over a month later, 1-2 weeks for the clutch & 3 for the sitting.)
Kind of frustrated that the local feed stores always sell chicks and ducklings in Feb and March, I can't even get chick crumbles after July without a special order.
In commercial houses light is fully controlled so the month doesn't matter, but my free rangers run by the sun.