Same shirt, different day.

German chancellor Angela Merkel was seen hiking in Italy wearing in the same red-checked shirt and khakis that she’s been vacationing in for the past five years. British Prime Minister Theresa May was also spotted wearing the same pink shirt dress twice during her own recent Italian tour.

These world leaders have so many pressing decisions to make day-to-day, it’s no wonder they’d want to simplify things on holiday to focus more on enjoying themselves, rather worrying over which blouse to pick.

Psychologists have even coined the term “decision fatigue” to address the mental exhaustion that stems from making a million daily choices, including what to eat, which route to take to work, which emails to answer first, what to read, what to watch, which pic to post on Instagram, which cereal to buy – and what to wear. The more choices you make throughout the day, the more you drain your willpower, and the harder it actually becomes to make decisions – so you default to the easiest option, rather than the best one.

“Some people save their energy [not choosing different clothes] so they can think about making other decisions,” Dr. Victor Fornari, a psychiatrist at Zucker Hillside Hospital in Queens, told Moneyish. “Or, clothes could simply not be very important to them, so they’d prefer not to worry to much about making decisions about things they don’t care about, saving their decision-making for things that they think are truly important.”

So it’s become quite fashionable for top decision makers to combat this daily brain drain by creating their own uniforms. Getting dressed becomes one less thing to worry about, which frees them up to invent the iPhone, lead the free world or create Facebook. Consider these monochromatic masters:

Facebook founder Mark Zuckerberg’s signature ensemble includes gray t-shirts, hoodies and jeans. “I really want to clear my life to make it so that I have to make as few decisions as possible about anything except how to best serve the community,” he said in a 2014 Q&A. Plus, it perfectly embodies the casual, athleisure-wearing Millennials who follow him.

First day back after paternity leave. What should I wear?

Posted by Mark Zuckerberg on Monday, January 25, 2016

Former president Barack Obama told Vanity Fair that he pruned his White House wardrobe to gray and black suits. ”‘I’m trying to pare down decisions. I don’t want to make decisions about what I’m eating or wearing. Because I have too many other decisions to make,” he said.

Albert Einstein, the quintessential genius, reportedly stuck with gray suits (and no socks) later on in life after his second wife passed away – leaving his gray matter free for more cerebral pursuits.

Country legend Johnny Cash’s all-black wardrobe was as much “The Man In Black’s” brand as it was his stage uniform. Originally, black was the only coordinating color garment that he and his backing musicians had to match on stage. But soon it became his persona, as he sang in “Man In Black,” that: “I wear the black for the poor and the beaten down / Livin’ in the hopeless, hungry side of town.”

Vogue creative director Grace Coddington has her finger on the fashion pulse, but she dresses all in black. “I don’t want to think too much about what I’m putting on in the morning,” she told Alec Baldwin in a WNYC radio interview. “I spend my whole life with clothes, and looking at clothes, and judging clothes, and considering clothes, and making clothes form into a story … so I want to have a clean palette on myself.”

Fellow fashion icon Michael Kors has designed himself a ready-to-wear wardrobe of black shirts layered under black jackets or blazers, and paired with dark pants. “What everyone is lacking in the world is time,” Kors wrote for “Time” last year. “So if you can find a uniform that makes you feel confident and comfortable in your own skin and you’re able to get dressed in less time, that’s a game changer.”

Apple CEO Steve Jobs always wore the same black turtleneck. (Justin Sullivan/Getty Images)

Late Apple CEO Steve Jobs infamously wore a black Issey Miyake turtleneck, Levi’s 501 blue jeans and sneakers every single day. He’d originally wanted all Apple employees to wear gray Miyake vests for unity, but when workers balked, he embraced a uniform for himself.

“Dunkirk” director Christopher Nolan mostly casts himself in blue shirts and black blazers, according to a 2014 “New York Times Magazine” interview, because, “He long ago decided it was a waste of energy to choose anew what to wear each day.”

And even regular folks have found adopting an everyday uniform to be life-changing. Personal finance blogger and HalfBanked.com writer Desirae Odjick told Moneyish she’s saved an hour and a half each week – and $1,000 a year – after #KonMaring her wardrobe for a daily ensemble that includes a silky, boxy-cut Express top ($30, in white and black) and a well-fitted pair of American Eagle skinny black pants ($50 apiece), which she tops off with blazers and cardigans. She has stuck with this look for two years now.

“It’s been the best,” said Odjick, 28, from Ottawa, Canada. “You know how when after you do laundry, for the first couple of days you wear your ‘favorite’ outfits that look and feel the best? It’s like that every day. It has saved me from those mornings when you’re later in laundry cycle, and nothing that’s left clean really matches, or it doesn’t fit right.”

That’s because, if you do this right, everything matches, and everything fits. And considering people regularly wear only 20% of their wardrobes, minimizing your outfits won’t just free your mind – it’ll also free up some closet space.

If you want to create your own minimalist, capsule wardrobe, Odjick suggests first identifying what you can get away with in your company. She writes in the tech realm, so skinny jeans and blouses are appropriate. If you need to wear suits or dresses, stock up accordingly.

Stick to neutral colors like black, white, gray and beige, which not only mix and match more easily, but they’re also appropriate for any occasion that comes up. And if you hate going to the dry cleaner, buy things you can machine wash.

Layering pieces also adds versatility. Her basic blouse and jeans uniform can be easily dressed up with a blazer, heels and jewelry, or made more casual with sneakers and a cardi. And this also takes the look from summer to winter.

Consider investing in more high quality cuts and fabrics, if you can spring for it, since you’ll want these pieces to stand up to being worn every day. “If you have a favorite pair of Old Navy pants that are only going to last a few months, but you’re OK with constantly replacing them, that’s fine,” she said. “Investing in pieces that will last for five years works great, too.

Finally, comfort is key; otherwise, it defeats the purpose. “I always feel confident in what I’m wearing,” Odjick said. “If a big meeting pops up unexpectedly, I’m not sitting there kicking myself that I would’ve worn something different if I would have known.”

And that’s one less thing to worry about, which is priceless.