Starting from November to January, all the carrier companies around the world have heavy loads, due to big deals during this period. Most airports in the US and Europe are overloaded, in addition, the instability of the weather (heavy snowstorms, ice).
Due to all these facts, flight delays are inevitable and, as a consequence, a shift in the delivery time of parcels. These are the realities of the peak season, not in our power to influence this.
But we had to warn you about this so that you could be safe, order everything you want with some margin of time and receive your packages before the holidays. Have a nice shopping!