Everyone counts it differently.
No stress at all.
I count first 7 days since seed touched soil a germination week. I just drop it straight, no fuss.
8th day is first day of week 1 of veg.
Flipping to 12/12 again, first day with duration of 12 hours - first day of flower.
But there is no rules, you will hear many ways . It makes no difference generally.....