Most egg laying and dual purpose chickens I've had started to lay between 4 and 5 months old.
Exceptions were 2 of 5 Golden Comets started before 17 weeks and 3 of 7 Barred Rocks and 1 of 5 ISA Browns started after 22 weeks, but before 24 weeks.
I currently have 8 Pullets 4 months old today.
2...