i am making a cake as close to the date as i can. I know that if you cover a cake in fondant it will keep for a few days but i am thinking i may just use buttercream. Should i keep a buttercream iced cake in the fridge overnight or keep it out at room temperature. Can you keep buttercream at room temp??? if so for how long???
How long will a fondant covered cake last if it has a layer of buttercream underneath?? im pretty sure storage of this type of cake needs to be outside of the fridge?

The particular butter cream recipe that I use is shelf stable (per my state laws, I can't sell perishable items) so I never refrigerate any of my cakes.

I make my buttercream one week in advance sometimes if I have a lot of orders and I store it in either airtight plastic bags or an airtight container right out on the counter. (air conditioned in summer)

You first need to determine if your recipe is shelf stable. Also the filling used in the cake needs to be taken into consideration.

What butter cream recipe do you use?

butter, icing sugar and a drop of milk plus flavouring like vanilla. I was not aware there were different recipes, do you have a better one? I will probably fill the cake with buttercream too rather than cream as i know that wont last.

there are a bunch of recipes here that are very good, I use Indydebi's or crusting buttercream and both don't have to be refrigerated

I use a couple of different ones also. Serious_Cakes has a great one too.....also found here in the recipe section.

The sugar to fat ratio is one determining factor as to whether or not it needs refrigeration.......as are the ingredients used.

All butter butter cream recipes tend to not hold up as well in the heat as the recipes that use either all shortening or 50/50 shortening butter.