You need to determine the exact tax rule in the state you live in.
Generally speaking, the dates are important at two points in a stock transaction.
The date you bought it. Along with all brokerage fees, this determines the value for tax purposes.
The date you sold it. This determines the net gain or loss, both of which have tax implications.
Generally speaking (check to make sure in your jurisdiction) "real" assets can depreciate over time while all other assets do not. So, say, a machine you use to earn income, you may be able to write off 20% per year (just an example) for the taxable value each year.
For other assets, like stocks and bonds, they neither wear out nor are instruments to earn income they are investments. So valued the day you buy and the day you sell and taxable on that basis in the same tax year.
It's a really, really crazy idea to ask these questions here on BITOG, or anywhere in the internets, for that matter. If you have tax and investment questions, ask someone who knows about these things and someone local so you get the right advice.
