How long can birthday cakes be kept at low temperature in the weather in the north?

It won't be bad for three days, but it certainly tastes much worse. If the storage time is too long, the cream will harden, and the longest is five or six days.

Because the cream cakes like birthday cakes you mentioned are usually cream formed by fresh cream. If this cream is left at room temperature for too long, it will easily sour and its shape will not look good. Refrigeration can preserve the delicious taste of cream and make the shape of cream not collapse easily. But eating the cake right out of the freezer will affect the taste. Because the cake itself is baked with eggs and cream and flour, if the temperature is too low, the entrance will not melt easily, forming a sticky feeling. So it is generally best to leave it at room temperature for several hours.