When do you switch light from veg to bloom with autos?

No need to change with autos, I've had mine on 20/4 since they popped.

Bonjour si ce sont des automatique je te conseil de leurs laisser 18H de lumière par jour elles passeront seul en floraison car se sont des automatiques. Si c’était des féminisé ou des fast, F1.. Je t'aurais conseillé de passer ta lumière en 12/12 a partir du 21 jours de végétation. J'espère que ces conseils vont t'aider bonne culture 😊

For my plant I switched it both lights on during week two I think? Because I read somewhere that your auto will take whatever it needs from the light anyway - and that in some cases it will make them grow faster with all the light on, so as long as both veg and bloom isn’t on you’re not using the lights full potential. I could be wrong - but in my case it worked wonders. Just remember to keep the lights a bit further away from your plant so you don’t shock it. My plant had some twisted leaves in the beginning after turning both veg and bloom on, but then it just took off with the growth. Good luck :)