Each bird will express molt differently based on their individual genetics. Chicks: at 1 to 6 weeks, 7 to 9 weeks, 12 to 13 weeks, and 20 to 22 weeks. A chicken's tail feathers are the last thing to grow in after the 20 to 22 week molt.
Adults: Can molt twice each year – in the spring and the fall – depending on the amount of available light. Roosters and hens also molt. The spring molt is usually very light compared to the fall one. A typical fall molt is approximately 7 to 8 weeks long, but anywhere from 4 to 12 weeks is considered normal. Keep in mind some birds go longer. Generally I notice a few more feathers for a bit in the house, around the yard and then one day it looks like someone had a pillow fight and busted open the pillows.
My birds tend to molt late fall into early winter here… it is all triggered by light. So Mr. Sunshine decreasing to just the right amount triggers the adult molt. Sunshine increasing in Spring the mini molt most folks hardly notice happens. My birds looked a little rougher in January then in February probably responding to the light increase. The faster a hen finishes molt the sooner she starts laying again.
I hope this helped a little bit, but it is a bit like waiting for each chicken’s first egg… we have to wait and see… I would mark the month the first time you see the feathers everywhere and look the hens over, everyday, try to determine who seems naked forever and which ones feather in faster, then pretty much expect the same next year.
PS they don’t usually loose all their feathers at once… but again genetics do weird things.
If it's spring they are unlikely to molt until day length shortens in the fall. Which could be anywhere from August to December depending on the individual bird.