Mine are a little over 7 months. One started Sept 3rd (so just shy of 6 months) and the other hasn't started yet and doesn't seem like she has any interest in it. I guess they just do it when they're ready.
Birds operate on a calendar all their own, and particularly with Wyandotte, the published ranges of when to expect them to start laying is very, very broad. I went looking today and found some sites suggesting as early as 19 weeks, while others suggest 6 months+, while still other usually useful sites leave that information off entirely.
"They will lay when they lay" and "Patience" is all I can offer as advice. My normal resources are failing me, and I'd not want to opine based on my birds, sample size is too small.