Is there a law about buying alcohol on your 21st birthday in California?

You are legally allowed to buy alcohol the day before your birthday! However, most establishments are not aware of this & won't sell to you until your birthday. Also, some liquor stores are so worried about being busted for selling to someone under age that they won't sell to you until the day after your birthday. Just go to a bar & your friendly bartender will even buy you the first one!