When do br's and slw's start laying?

[bryan8]

I have 2 br's and 2 slw's that are 19 weeks old. At what age do these breeds start laying?

 

[Katy]

I'm waiting on my SLWs to start....they're now 31 weeks old!

 

[Happy Chooks]

My BR started at 21 weeks.

 

[Tecalli]

My barred rock is now 23 weeks old and no egg yet.
I was getting really impatient but then I read on BYC that overall health wise (problems related to laying) its better for them to be late bloomers than early starters. That info really helped in me getting over my impatience.
I am not adding artificial light so she is only getting about 11 hours of daylight currently, so I have low egg laying expectations.