I made a fresh patch of buttercream yesterday

My buttercream recipe

250g Butter
5-6 Cups of Icing Sugar (so you know using a 250ml cup for each cup)
4 Table spoons of Milk

It has been in and out of the fridge all day yesterday and I wanted to use it today on cupcakes, how long will it keep for and can it stay out of the fridge or does it have to be stored in the fridge :S

It should be fine. The butter doesn't have to stay refrigerated and there's enough sugar to keep the milk safe.

For my frosting recipe I use butter, PS, and heavy cream and I've had no problems leaving it out.

Thanks everyone guess I just always second guess myself need to be more confident