"Capital gains" occur in the tax year when you sell your shares and take a profit on them. As long as you simply hold them, there is no tax treatment of them one way or the other. The IRS does not expect you to pay taxes on "anticipated gains" when nobody can possibly know what those gains will be or when you plan (or are able) to realize it.
Until or unless you sell the shares, there's no way to know if you actually will see a return on your investment, although that's a totally different topic.
Thanks to JoeTaxpayer for pointing out what I was missing in your question!
I doubt the clock would start until at least the point at which you receive your share certificates, since you have yet to be given them. At the moment you have nothing more than a promissory note of shares in exchange for your investment. The "taxability" (let me invent a word here!) of your investment first presumes you have an ability to sell that share position and realize either a gain or loss, and you cannot since you don't have the certificates in hand (or however they're being delivered to you).
I hope this helps.