'zuo tian xing qi liu'(昨天星期六) that is enough 'le' is used together with verb,for example 'zuo tian ta zou le'(昨天他走了)

le is no use in here

You can say "zuó tiān (shì) xīng qī liù " or "zuó tiān (shì) lǐ bài liù " ("shì" can be omitted) saturday = xīng qī liù = lǐ bài liù I hope it helps. ^^