When the seedling breaks the soil you can start counting. Keep in mind they estimate 65 days , but be prepared for it to take a week or 2 longer if conditions aren't optimal . Also depends how much training you do. LST is recommended for autos to bush them out and keep the canopy level and improved yield. Theres plenty of tutorials out there.
I find 35 days my autos will veg for then they will flower for another 40 to 50 days. But that's with a lot of training and defoliation . Some will be done sooner. Hope this helps π±π