Flowering Time Definition?

"Flowering time"--does it start when you switch to 12/12 or when they actually start to show their sex?

Also, I have a two chamber setup: veg and flowering. I'm running a 150w CFL light in the veg chamger. Can I sex the plants in the veg chamber (12/12 CFL) before moving them to the flower chamber?

12/12 is when you would count it saits its an 8 week strain it would start when you lower your hrs of light form 18/6 or 24/24 to 12/12