It’s one day only, folks! 

Someone standing outside 11 Wall Street on Friday might have been surprised: yes, the traders at the New York Stock Exchange were wearing blue jeans.

In celebration of the Gap’s (GPS) 40th anniversary, the company has given away 1,200 pairs of jeans to NYSE traders, a promotion for the new line of Gap 1969 Premium Jeans. 

This was the first time in exchange history, and may have been the last, that traders could wear jeans.

While many loved it, like Christopher Trimble of McCauley Securities who said he’s “very comfortable” in his new 1969 denim, some others are complaining just a bit. Traders were told to adhere to the rest of the NYSE formal dress code, which includes a button-down shirt, top button buttoned (no exceptions), a tie and jacket.

Christopher Martin, CEO of Greywolf Equity partners says “while I like the concept, I walked out of my house and it was 85 [degrees] and muggy, a little uncomfortable for denim.”

Danny Ryan of DRD Securities added, “it’s a nice change to wear jeans” but says he’s old fashioned and likes wearing a suit to work. “You’re more productive when you’re dressed in proper business attire.”

Photographers and free standing billboards of Gap Models in jeans were plastered around the NYSE Friday morning in celebration of the collection named in honor of the Gap’s debut year, 1969. The Gap store at 58th and Lexington Avenue, in New York City on Thursday night had a live band jamming in the store for the 40th anniversary.

North America president Marka Hansen, along with Bob Fisher and fellow founding family members John Fisher and Bill Fisher, will ring the NYSE closing bell remotely from the company’s headquarters in San Francisco Friday afternoon.   

Gap stock was trading higher Friday on its quarterly report, and is up more than 40% year to date.

One last thought on the jeans: Benedict Willis III of VDM Institutional Brokerage, who was not wearing jeans on Friday, said: “If this is the Cathedral of capitalism, you wouldn’t expect to see the Pope in blue jeans.“

--Nicole Petallides is the New York Stock Exchange Anchor for FOX Business Network.