I've heard there's a "wacky hair day" in western culture. Then does it somewhat related to the "bad hair day?"

Native speaker’s answer
Rebecca
Primarily in the USA, schools and public institutions would occasionally have a "wacky hair day", which is a day where people were expected to style their hair in "wacky" ways and would not be judged negatively for it. There is a slight relation to "bad hair day" as an expression, specifically the name of the event being inspired by the expression, but "wacky hair day" itself is not used as an expression. It is uncommon for institutions or schools to have "wacky hair days" anymore because many people, especially younger people, chose to style their hair in unconventional ways to begin with. Ex: Did you see how she came to wacky hair day? She looked so wacky! Ex: I'm having such a bad hair day, good thing it's wacky hair day at school so no one will notice!