其實這是一直的 common knowledge 。
Skirts, Dresses, and Skirted Suits
Dresses, skirts, skirts with jackets, dressy two-piece knit suits or sets, and skirts that are split at or below the knee are acceptable. Dress and skirt length should be at a length at which you can sit comfortably in public. Short, tight skirts that ride halfway up the thigh are inappropriate for work. Mini-skirts, skorts, sun dresses, beach dresses, and spaghetti-strap dresses are inappropriate for the office.