An unknown person visited this website as a consequence of the search engine query "When does winter really begin?" I find this question to be extremely poignant, even poetic, and I regret that sublethal.net never actually addressed it.
Of course the prosaic answer is that in this country it's customary to consider the winter solstice the beginning of winter, although some cultures call that the middle of winter. I think it's the shortest day of the year, which is definitely in its favor. I believe all days should be a good deal shorter, and some days shouldn't exist at all. We have seasons because of the earth's 23 degree tilt, if I remember correctly, and so that Stevie Nicks has plenty of metaphors to work with. But anyway there are other possible answers to the question, such as:
Winter begins when all hope is lost.
Winter begins when the icy wastes in one's soul gain ascendancy over the smiles of a summer night etc etc.
Winter begins when you close your eyes.
Winter begins the day you are born.
Winter has always already begun.
Winter begins when summer's dead fingers are pried from life's throat.
Winter begins when autumn gives up its ridiculous pretenses.
Winter begins just as you are starting to really live!