La comida es para el sábado.
though i correctly translated it as "the food is for saturday" i wonder why "el" is used in the sentence?
It's because in Spanish and other romance languages, the article is used to define the object. "The food is for the saturday." It can be extrapolated to mean: "The food is for [this] Saturday."
I think it distinguishes it from "La comida es para los sabados" (pardon my lack of accent), i.e., "The food is for Saturdays". If you have a food that comes back on the menu every Saturday (like Grandma's fruitcake gets recycled every Christmas!) then you would need "los sabados", right?