I agree mofoo, Like I mentioned that evey baby I stuck out that was on 18/6 went into flower while the ones I had on 16/8 continued to veg for till normal time. Don't get me wrong, a early harvest is always nice, but I dont want 4ft tall plants, i want my 12ft tall trees.
16/8 is a veg photo period and was the recommended photo period for veg when i started growing
18/6 became popular in the mid 90s
24/0 became popular in the 00s
strange you notice a difference outdoor
indoor i veg my plants on 16/8 or 18/6 they go into flower just the same when flowered
on 14/10 they grow a little more before flower sets in
what i have noticed made the most difference for me was taking cuttings from a rejuvenated plant
these cuttings are always in a state of heavy preflower and will flower quickly in a few days
in a week small buds
peace