7. Royal Women Must Wear Tiaras After 6 p.m.
There’s a very specific rule about when royal women can wear tiaras: only after 6 p.m., and generally only at formal events. During the day, hats are preferred. Tiaras are symbols of marriage and status, so unmarried women traditionally wouldn’t wear them. This strict etiquette has deep roots in royal history and continues to define how female royals dress.