Don’t count the days.

Tallying them, like etches on a prison wall, will only serve as a reminder of how interminable the coronavirus quarantine is, how insufferably abnormal, each mind-numbing day building unmercifully into a contagion of its own.

“I have no idea how many days I’ve been in quarantine. None,” said Scott Kelly, the former NASA astronaut who spent 340 days in space, the record for the longest single spaceflight by a U.S. astronaut. “I don’t think about it. I just think, this is my reality. This is my mission. And it will someday be over.”

Today, instead of being confined on the International Space Station with a handful of crewmates, he’s restricted to his 1,200-square-foot, two-bedrooms-with-den apartment in Houston with his wife. But his philosophy is the same, as is his strict adherence to routine, laid out daily on a shared Google calendar. He sets his alarm for 7 a.m., eats breakfast, “then work goes to noon, and then lunch, and then work, and then physical training, then plan for the next day, then dinner, then free time.”

Astronauts have a lot to teach us about how to survive the great covid-19 lockdown of 2020. So do explorers and scientists. And the researchers who study them say their experiences — confined in a spacecraft in orbit, a ship at sea or an outpost in Antarctica — can shed light on how we can best navigate an unsettling time that in its darkest moments can feel like an unjust incarceration.

Since the outbreak hit the United States, astronauts have been eagerly offering up their wisdom, urging those of us not used to forced isolation and social distancing to exercise, stay productive and be positive, find creative outlets, revel in nature, stick to a schedule, reach out to loved ones, and reconnect with old friends.

But don’t count the days, at least according to Kelly. In space, like now, he assiduously tried to will himself into a tolerable ignorance despite repeated reminders of milestones — 100 days to go! — from ground controllers and crewmates.

“Drove me crazy,” he said.

NASA has long been interested in human interactions among astronauts, especially as it looks toward long-duration spaceflight, when people could be cooped up together for long periods. Between 2003 and 2016, it selected astronauts to keep journals that would then be analyzed. The project was led by Jack Stuster, a psychologist and anthropologist who had researched the behavior of explorers, such as Ernest Shackleton, who had led long-duration missions to remote corners of the Earth, and wrote a book about it titled, “Bold Endeavors.”

After reading the astronauts’ diaries, he concluded that they “share an unusually well-developed sense of self-awareness.” Which came as a bit of a surprise.

He had read “The Right Stuff” by Tom Wolfe, about John Glenn and the rest of the Mercury 7, and so Stuster had thought astronauts “tended to be overly confident and certainly unwilling to admit to possessing flaws or normal human frailties.” But instead, social distancing for long periods in orbit revealed that even NASA’s finest were endearingly human, prone to bouts of brooding and pity parties like the rest of us. The alchemy behind the “right stuff” has long been misunderstood, it turns out — teaching NASA to go lighter on the bravado and heavier on the patience and compassion.

“What a day it has been,” one astronaut confessed into the assigned diary. (All the participants did so under the agreement that their journals would remain anonymous.) “Today started with urinating in the bag so that set the tone for everything.”

“I think I do need to get out of here. Living in close quarters with people over a long period of time, definitely even things that normally wouldn't bother you much at all can bother you after a while,” wrote another. “That can drive anybody crazy.”

“I could tell there was some stress in the air because there were a couple very short tempered exchanges between us this morning,” wrote another.

On his longest spaceflight, former NASA astronaut Terry Virts spent 200 days on the space station. “That’s a long time,” he said. Long enough to know that a small annoyance “is like a pebble in your shoe. If it’s a couple days, it doesn’t matter. But over a long time, that pebble is going to start to cause problems. So you have to talk things through, which is not always fun and comfortable.”

(In that case, let the record reflect that this reporter may have left a half-eaten banana out amid the clean dishes drying on the kitchen counter. This not only posed a sanitary issue, but the reporter should have remembered that his wife absolutely cannot stand even the smell of bananas. He apologizes.)

Stuster said there are similarities between coronavirus quarantine and a long sea voyage gone awry. (While he’s never studied the particular anthropology and pathos of cruise ships, they might be fertile ground for inquiry as the pandemic leaves many stranded at sea.) In 1898, an exploration team locked in Antarctic ice suffered through the winter by holding beauty contests of illustrations of women ripped from magazines in the ship’s library and got exercise by taking what they called a “madhouse promenade” on the ice around the ship.

“They had senses of humor back then,” Stuster said.

To prepare for long-duration spaceflight, NASA has been working with the University of Hawaii, which has been simulating Mars missions by confining small groups at remote outposts for months at a time to study how they interact.

One of the coping mechanisms crews developed was to celebrate everything — breaking up the mundane with holiday-like events that turned half birthdays and even National Hot Dog Day into parties to look forward to.

“Anything they can do to make a day special,” said Kimberly Binsted, a professor at the University of Hawaii and the principal investigator of the Mars simulation project.

Today, during the novel coronavirus pandemic, chefs are leading lessons on how people in quarantine can cook what’s in their pantry. And newspapers, such as this one, are running stories like: “Making yogurt at home is easier than you think.” Or: “It’s time to relax and figure out how to mix a drink with what you have."

When Binsted was on a mission in the Arctic, one of her crewmates from Quebec was getting homesick. So one Sunday, they made him poutine, or their best approximation of the French Canadian dish, given what they had.

“It took forever because we didn’t have potatoes, so we had to reconstitute these scalloped potatoes from a box and fry those,” she said. “We made cheese from dehydrated milk, and eventually presented him something which was only slightly like poutine.”

Binsted insists the hydrated, reconstituted vaguely poutine-esque concoction, awful as it sounds, was actually tasty.

Recently during “Yuri’s Night,” a celebration to commemorate Yuri Gagarin becoming the first person in space, Kelly had a video conversation broadcast on the Internet with Bob Weir of the Grateful Dead about space, isolation and music. Weir had spent years on the road touring, and Kelly asked Weir what advice he had for those in quarantine.

“File off the edges,” Weir responded. “Because if you have rough edges, there are going to be some scars.”

Music, Kelly added, is also important. On the space station, the crews would get together for dinner on Friday and Saturday, and he would play music on his iPad.

“I have pretty eclectic taste, from classical to rap,” he said. “I’d often bring Coldplay, Pink Floyd, sometimes the Dead. The cosmonauts loved whatever I brought to those dinners. But I’m curious — if you were on the space station right now on a Saturday night, what album would you want to play?”

“Probably it would be Miles Davis’s ‘Kind of Blue,’ ” Weir said. “Everyone loves that, from the first notes of the first song, ‘So What.’ ”

It’s a track that starts slow, disorganized, then builds out a theme — bass, piano, drums and then that trumpet, both plaintive and celebratory, the kind of tune you can listen to over and over and still hear something new. An anthem for a quarantine.

Isolation blurs the lines between monotony and boredom, solitude and isolation, loneliness and being alone. But the distinctions are important. No one knew that better than Michael Collins and Al Worden, two NASA astronauts during the Apollo moon missions who stayed behind in orbit around the moon while their crewmates walked on the lunar surface.

Throughout their careers, both were asked whether they were lonely.

“You can be lonely anywhere,” Worden told The Post in an interview last year before his death. “I can be lonely right in the middle of town. Being alone means there’s no one else around. Now I know I was alone in lunar orbit for three days, but I was not ever lonely.”

Likewise, while Neil Armstrong and Buzz Aldrin pranced on the surface of the moon, and Collins flew on the far side out of radio contact with Earth, he thought, “I am alone now, truly alone, and absolutely isolated from any known life. I am it.” For those keeping score, he wrote, that would be “three billion plus two on the other side of the moon, and one — plus God knows what — on this side.”

Former NASA astronaut Frank Culbertson was the only American not on Earth during the attacks of Sept. 11, 2001, and endured his own version of isolation. Traveling in the space station some 250 miles high, he could see the column of smoke rising from New York City, where the twin towers had been hit. A former naval aviator, he snapped into action, taking photos and relaying what he was seeing to the ground in case another attack was being planned. Still, he felt a disorienting sense of detachment, compounded by dread and helplessness.

“It was a feeling of isolation and frustration that we couldn’t do more to help the people down on Earth,” he said.

Wernher von Braun, the legendary NASA engineer known as the father of the Apollo-era Saturn V rocket, wrote in the 1950s that on a lengthy trip to Mars, even “little mannerisms — the way a man cracks his knuckles, blows his nose, the way he grins, talks or gestures — create tension and hatred which could lead to murder.”

In one of his astronaut studies, Stuster concluded that “such a grim outcome is unlikely.”

And indeed, last week, NASA’s crew on the space station seemed to be getting along quite well. During an interview with reporters they were gracious and friendly and even ended with a synchronized, weightless backflip, arms locked together.

Still, Jessica Meir, who had been on the station since September, said it was “quite surreal for us to see this whole situation unfolding on the planet below.”

From space, she said, there were no visible signs of the turmoil the pandemic is causing.

“We can tell you that the Earth still looks stunning as always from up here,” she said.

Chris Cassidy had just arrived for this third trip to space. Normally, astronauts spend two weeks in quarantine before launching to avoid bringing bugs to the space station. He knew that was going to be the case again for this flight.

What he didn’t know, he said, was that “the whole rest of the world was going to join us.”