What Week Is This?

Determining when to do something, like beginning to feed plants, transplanting them, trying to influence their eventual sex, topping them and so on, seems to depend on how many weeks old they are. But there doesn't seem to be any consensus on just when you begin counting. Is it when you start germinating? When the seeds crack open? When the seedlings first pop out of the soil? When they get their first pair of true leaves? Their second? Their third or even fourth? Also, when told a certain strain should vegetate six weeks or fifty days or whatever, when do you start counting?

Well the different responses are because there are so many factors that are involved its something you have to figure out yourself.
Some of the factors that change the timing are.
Strains you are growing.
Grow method FIM, SCROG, SOG, mainlining, topping, lst ........
What your growing in hydro, soil, soilless........
Lighting, Temp in the grow room and on and on and on.....

I grow in roots soil it has enough nutes that I don't feed at all for the first 3 weeks or so of veg.
Seedlings don't need any food at all just light.

NOTHING you do during growth will influence sex. <---other then stressing a plant into going hermie
I have been told by a professional breeder higher temps during germination will cause more males.
Not sure if this is 100% true or not, but I tend to believe him.
I have always germinated seeds at 76 degrees and get about 80% female.

I always count the days of veg from the day the seedling breaks the soil.
I count the days of flower from the day flowers start forming usually 2-3 week after onset of 12/12.
Now im not talking about pre-flowers but actual flower formation.

As far as transplanting you want to do it before the plants get root bound.
In my case I veg in 1gal pots for 3 weeks transplant into the final pots usually 5-7gal.
I veg for another 1-3 week then its off to flower.

Here is a good read on when to harvest. https://www.rollitup.org/subcools-old-school-organics/66405-amber-alert.html
Its another thing that you will need to figure out, the above is well written and gives you the when's and why's of harvest timing.

Thank you for the thoughtful reply, budfever, you made me realize I should have included information about what I'm doing. I grow outdoors in my yard using containers of the same capacities as yours, 5 and 7 gallons. I move them around my yard to get them enough sun. This season I've started 4 each of Northernberry, Skunkberry and Cinderella 99. To keep things inconspicuous I try to start with as few plants as possible but as many females as possible. I was reading something on the Dutch Passion web site about doing what you can to influence a plant's sex and they claimed it's determined in the 3rd and 4th weeks. I also read that it happens at the 3 pairs of leaves stage and continues for three or four weeks. According to them, some of the factors that promote females are, as you said, cooler temperatures and also more nitrogen, higher humidity, fewer hours of light and deep cups for the seedlings. I don't know how much of this really helps, but I'm trying whatever I can.

I kinda asked some of the same questions in my thread I just started. Good info budfever