re: need help finding a stocks share price on a specific day

The fair market value on the date of the gift is the mean between the high and low prices on the date of the gift, not the price at close.

But your cost basis and holding period is the same as the person who gifted it to you. The cost basis and holding period transfers.

So if the person who gifted it to you bought the stock for $100 in 1964 and you sell it for $1,000,000, you'd have to pay taxes on $999,900 of long term capital gains.

The fair market value matters when it is below the original cost basis on the date of the gift. For example, if the person who gifted it to you paid $1000 for it but it was only worth $500 on the date of the gift. In that case the fair market value on the gift date becomes your cost basis and your holding period begins then provided you sell at a loss below that fair market value. So your cost basis would be $500 and you'd take a $100 loss if you sold for $400.

If you sell at a price between fair market value on the date of the gift and the original cost basis, so between $500 and $1000 in my example, no taxes are incurred. But any sale above the original cost basis puts you on the hook for taxes on the profit above the original cost basis.

Schwab on gift tax issues

Code of Federal Regulations on determining fair market value of stock gift