MINNEAPOLIS — It was 4 a.m. on a recent Sunday.

Long after U2 melodies and the buzz of weekend bar-goers had faded in Stadium Village, Eyob Weyu sat alone in Moos Tower, hunched over a calculus textbook and a large cup of coffee.

While many of his University of Minnesota classmates braved large crowds in Dinkytown and Stadium Village on a recent Saturday night, Weyu was putting up his own fight to get through another all-nighter in Moos Tower.

He and others do it nearly every night.

“After college, many people will look back and wish they could’ve done better,” said the pre-medical junior, who eventually left Moos Tower at 8 a.m. “I really want to do well so I’m willing to sacrifice everything.”

One of the last to leave nearly every morning, he is often physically alone in the building. But his sacrifices — sleep, social life and time with his family — are not rare.

That morning, economics senior Victor Llapa sat at a table feet away facing Weyu. The sun was not yet up.

“A lot of students do this,” Llapa said at 5 a.m. “Personally, I don’t have a choice.”

Llapa, who keeps a schedule of three or four overnight study sessions per week, and Weyu have developed a bond over their similar study habits. They wake each other up from naps and let one another back in the building after it closes.

It’s part of what Llapa calls the Moos Tower “all-nighter society.”

Weyu said his summer schedule feels natural. After the sun has fallen in Minneapolis, it’s daytime in his native Ethiopia, he said.

He sleeps just four to five hours each day, often in his car between studying sessions and classes.

But these late night habits stem from more than time zones.

He stays up all night before going to class from 8:30 a.m. to 3:30 p.m. because he simply can’t fall asleep without completing all of his work.

“I guess I’ve always been this way,” he said.

Llapa agreed, adding that the dozens of students he has encountered late at night share that trait.

“It would really bother me to go to bed with work unfinished,” he said.

Llapa, a self-professed “night person” who works 40 hours each week and goes to school full time, said this is the only way he can manage his time. Spending Sunday, Monday and Thursday nights in Moos Tower is the only way to stay on top of his workload.

Fan Yang, a junior in the department of computer science and engineering, said she was surprised to hear people stay in University buildings so late after finals have passed — especially on weekends.

Yang pulled one all-nighter as a freshman and said she’ll never do it again. She always thought the root of all-nighters — procrastination — was something she avoids by working weekends and early mornings.

“Most people stay late because they have to,” Yang said. “That’s college.”

But Llapa insists it is more than obligation that keeps him coming back to Moos Tower regularly for overnight study sessions.

“We have a passion to learn,” he said. “I don’t just want to get a good grade, I want to understand everything and take something away from this experience.”

Ricky Carlson has been a facilities worker at the University for 25 years.

He has spent 20 of those years in Keller Hall, which he said is a hot spot for overnight research and study groups.

“I’d imagine just about all students have spent the night in one of these buildings at one point or another,” he said recently pointing to a student doing research in a lab at about midnight.

He said the peace and quiet that comes after 10 p.m. creates a productive atmosphere that draws many students.

Wenhao Liu is one of them. He’s in the process of transitioning from an early riser to a regular all-nighter, an effort to make time to study for the Graduate Record Examination this fall.

He said his favorite part is the solitude he feels knowing he’s one of only a handful of people on campus.

“It gets a little lonely,” he said at 1 a.m. as he was just getting started with his work. “But I like it that way. It’s not bad.”

Hours before, Chad Lajiness sat in the same chair that Liu occupied in Keller.

He had a different take on all-nighters.

“I quit learning after a certain point,” he said. “If I’m not done by midnight, I quit and try again later.”

He left Keller Hall well before 10 p.m. recently.

Jia Wen has never pulled an all-nighter.

The graduate student in the department of electrical and computer engineering said the key to working efficiently is sleep, and she gets plenty of it by going to bed on time and waking up early to complete her work.

She stays productive by taking the “home” out of homework.

“I never study at home because home is a place for enjoyment,” Wen said, “not for studying.”

Many of Wen’s friends share her attitude of getting out of the house. They work in University buildings past 2 a.m. several nights each week, she said.

“These students aren’t weird at all,” Wen said. “Maybe they just do this because they love it.”

But she also said there is nothing she loves more than her health, a casualty for students in the “all-nighter society.”

Wen said her roommate is a prime example — the regular late-night studier has sought medical advice for changes in her eating and mood patterns.

After more than two months, Weyu said his summer schedule has begun to catch up with him.

“I feel tired all the time,” he said.

Llapa, on the other hand, said he has found a way to organize his life so he’s not forced to sacrifice too much in pursuit of future success.

“It’s all about balance,” he said. “I work hard during the semester, so once it’s over I can enjoy myself.”

At the end of the summer, he plans to organize two weeks of swimming, camping and drinking — but not that much, he said. He’s already invited Weyu and a handful of the other late-night regulars who have shared his stress throughout the summer.

But Weyu’s break will be short-lived. He already has his books for the fall semester, and he said he plans on getting a jump-start on the material before classes begin.

“I don’t want to disappoint my family,” he said.