12 12 when to count

Hello. Im wondering when I should start counting when in 12 12.

Im doing 12 12 from seed BTW (25 days old) and my plant showed around 20 days old and now today has severals hairs coming out of most of the nodes on the plant.

Should I start counting now or do I wait until I have bud sites formed?

I start counting the day after I switch to 12/12. Usually strains are rated in days of flower from when 12/12 starts.