I love how 5 people post when the OP asks a serious question and not one person can help the OP out. You can divide the growth of marijuana into 3 stages, germinative, vegatative, and flowering.
Germinative is from when you add water till the first leaves appear, not very long
Vegetative is when the plant grows without budding. This happens during the spring (longest days of the year)
Flowering is when the plant will start to produce flower, or buds. this happens during fall (shorter days)
If you grow inside, you can give it light 20 hours a day during vegatative. Once you switch it to 12 hours a day it will start budding.
If you grow outside it will follow the seasons UNLESS you get an auto-flowering strain. These strains will flower once they're mature, and disregard the season/light times.
Hope this answers your questions. Pm me if you have any other queries.