Well one of the things I've discovered since I got my chickens back in May is that all this business about chickens laying at "around 20 weeks" is kind of subjective. In going to the feed stores and farmer's markets locally and talking to a number of other chicken keepers, the general consensus is that I am being impatient and that with the exception of a few breeds, it is extremely rare for most laying hens to produce an egg before the age of 6 to 7 months. So if your birds were hatched anytime in March, you could be waiting as much as another month. I am also told that if they do not lay before the 1st frost, they won't lay until the following spring.
My leghorn is out in the henhouse right now singing her head off SO LOUD I could hear her from all the way up here in the house with the door closed and the water running in the sink. Could it be I'll have an egg today?? She's an almost 21-week-old leghorn--purportedly was supposed to start laying about a month ago (leghorns generally start at 15-18 weeks, or so I have been told & they are one of the few breeds that do lay before the age of 6 months). I got her specifically because she supposedly would start laying at about 16 weeks. Well, she was 6 weeks old when I got her, and she's been here 15 weeks as of tomorrow, so what do I know? LOL!
I have read stories on here, though, of people having barred rocks and EEs and RIRs laying at anywhere from 18 to 22 weeks. Maybe it has something to do with what part of the country one lives in and the different climates, etc.? I dunno, all I know is that every single chicken keeper I've talked to at the farmer's market, in local feed stores (including one fella that's been raising RIRs and NHRs for 40 years), and a few I met last weekend at a poultry auction have all told me to stop being so impatient and not to expect any eggs before the birds get about 6-7 months old. I may have another month or so to wait, so I've stopped doing the egg check 5 times a day and only do it twice--in the morning when i let them out, and in the evening when I put them away in the henhouse. And even, then, it's not a "serious" egg check... kinda more like "just in case".
In the interim, I'm having fun spoiling my chooks and hanging out with them in the yard. They are great and awesome pets! Who ever woulda thought I would fall so in love with these dang birds?? hehehe.