Advent Calendar for Adults - Finest Sea Buckthorn Liqueur. Advent, Advent, your throat is burning – we have the solution: Our Advent calendar for adults, filled with fine sea buckthorn liqueur. This is the perfect way to enjoy the wait for Christmas. Produced according to the time-honored recipe of the Spreewald Spirits Manufactory. Since this product has an alcohol content of 17% ABV, it is illegal to sell it to persons under 18 years of age.