I suggest it could be many things but what is most important is what you decide to do with the large amount of energy available leading up to this day. Make a decision how you want to utilize this energy like fuel to create and to join with others in creating what is worthy and farreaching. Your heart has very clear and strong knowings about your truth and your values and it always awaits for you to create in alignment with what lives in the very center of your Being. If you did nothing in your life other than locating just what is the truth of your heart and it's values, it would be a life well spent.
I suspect that your heart knows far more than your head about what is important about Dec. 21 for you personally. Whatever you resonant with about the meaning of this date, so long as your heart casts it's vote, you are in good shape. This is not a matter of who is right and who is wrong about the meaning of the date. It is more playful than that. It is about, what lightens you up and let's more love of life stream through as you go through a kind of birthing process.
Personally, I like the idea of the date being a stepping through a portal in which one set of limiting beliefs is left behind and a new set of expansive beliefs is adopted. Things like time travel and dimensional shifts and the feeling of unity with the ALL are on the other side of the portal. You do not have to walk through. You can keep the limiting beliefs but the opportunity to shift quickly and well may never again be so grace filled and easy. Life is always about shifting and growing, but this is different.Just about everyone feels something big is up. The tendency for many is to think it will be an external event. I think primarily it is about an internal 'change of heart' and out of that, external changes will show themselves. It is already happening. But there is more to come. Much more. Much much more.
This is humanity's big chance. I suggest you open wide to whatever form your experience takes. You'll be glad you did.