personally i don't think you could have planted much later than you did,during dark time weed produces a chemical which is quickly diminished by light,when the chemical reaches a critical level,flowering is induced,(providing it's sexually mature which most plants are by 4 weeks,alternating nodes)indoors you achieve these levels when you switch 12/12,hence the reason it's important not to have light leaks growing indoors but outdoors thing are a bit different,the days get naturally shorter so flowering doesn't necessarly doesn't need 12 hours dark,outdoor plants actually don't mind low levels of light during dark time,ie moon streetlamps etc,mine started flowering while we were getting 13.5 hours-14 hours light and i have lights from the football park shining in my garden until 11.30pm,on indoor grows i've actually put seedlings straight into 12/12 and they started flowering at 2 weeks,gave a bit over an ounce by end,but in my opinion planting later is only going to affect the size of your plants when they finish flowering,you just gotta watch out that you don't leave it too late as you do require a little veg time so they can reach maturity,don't want to get stuck waiting for them to mature and really want them to be flowering by mid september at latest so they're done by end of november,before winter sets in
but that's just my opinion,which may well be a load of rubbish