The Casual Friday reference article from the English Wikipedia on 24-Jul-2004
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Casual Friday

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Casual Friday or Dress-down Friday is a semi-reprieve from the constrictions of a dress code that some offices celebrate. Whereas, during the rest of the week, business shirts, suitss, tiess and dress shoes are the norm, on Casual Friday workers are allowed to wear casual dress. Some companies allow jeans, T-shirts, and sneakers but others require smart casual dress.

Some companies and schools operate an occasional "dress down" day, where employees pay a small fee to be allowed to wear casual clothes (or even fancy dress); the money being donated to charity.

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