No, and it's not a noun grammatically, but an adjective. See for example рабочий день - working day.

Another example where you would expect a noun is "host" (as in talk show), where the Russian word is ведущий, something like "he who leads". It happens rather frequently. You may have noticed the word for "weekend" or "days off work", выходные, which is also just an adjective in plural. These words decline like adjectives, not nouns.