Olivia Wilde Describes Her Hellish First Mother's Day

"We were sweating and angry and hungry," Wilde said of her would-be celebration.

June 18, 2014 -- Olivia Wilde loves being a mother.

Her first Mother's Day celebration however? Not so great.

Wilde, 30, who welcomed a son, Otis, with fiancé Jason Sudeikis in April, told David Letterman that her plan to have an idyllic picnic in Central Park went horribly awry.

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"I had this image of Central Park as being completely empty, just rolling meadows, with one person a mile away flying a kite, and some balloons," she said. "We go up there and it's hell. ... Everybody in the world is in Central Park that day. .... It also happened to be Japan Day, which it turns out is a huge deal in New York City."

Even worse, Wilde explained that she could only find one bathroom. By the end of the experience, when both she and Sudeikis, 38, were "sweating and angry and hungry," the actress found herself changing baby Otis's diaper in public.

"I finally just dropped to the ground on a patch of dirt, like in between two ugly roads, and [was] just shaking," she recalled. "Then [I] just ripped off the diaper of the kid to change him and he just pooped everywhere—like a torrent, a flood."

Still, she has high hopes for next year's celebration, and hasn't given up on the holiday altogether.

"It was really cool," she said. "I now consider it the most important holiday of the year."