Is that a dress or a nightgown? Yes

Sleepwear for a day or night out is not only now acceptable, but it is also apparently "in" for fall.

Only Hearts, a New York City- and Los Angeles-based boutique, has been selling lingerie and loungewear to be worn anywhere, anytime for decades. The retailer even trademarked the phrase "inner outerwear" in the 1980s.

But Columbus Avenue store manager Andriette Flemings said that people are buying into PJs to wear all the time now more than ever.

"Women are coming in buying slip dresses, chemises to wear as dresses," she said.

The trend skews from low to high. H&M sells a flannel shirt dress for $25. A.L.C. has a silk pajama-shirt-inspired dress for $495. And the New York Times T Magazine recently featured an $8,600 Givenchy nightgown dress in a piece called Fall's Nightgown-Like Dresses in the Light of Day.

"There's a lot of velvet, there's satin and people are also layering them," said stylist Lindsey Brooke Weiss, who runs the fashion blog

Weiss said she agrees sleepwear-inspired looks are sticking around for now and recommended layering as temperatures cool.

"I think it's just really yummy to have a satin or lace camisole or a slip dress with like a big, fluffy shearling-like jacket over," she said.

On an unseasonably warm late September night, Sarah Beth Samuels was strolling on East 86th Street wearing a kimono-like robe over jeans.

Yes, she said, people often ask if she's wearing her robe. No, she doesn't mind.

Because the thing about wearing sleep-inspired wear out is that you're comfortable wherever you go.