An outdoors sign for Walmart is seen in Duarte, Calif. Tuesday, May 28, 2013. Wal-Mart Stores Inc. pleaded guilty on Tuesday to charges the company dumped hazardous waste in Calif. Wal-Mart entered the plea in federal court in San Francisco to misdemeanor counts of negligently dumping pollutants from Walmart stores into sanitation drains across California, a company spokeswoman said. (AP Photo/Damian Dovarganes)

In her nearly two years with Walmart, Maya'Neisha Johnson has typically worked about 20 hours a week at her Western Arkansas store, while pursuing a bachelor's degree. But lately, when her class schedule permits, Johnson has managed to pick up an extra shift or two a week, often logging more than 30 hours.

For Johnson, who's 20 years old, the additional hours are significant. They mean not only a bigger paycheck but also more on-the-job experience outside the apparel department.

"I've added anywhere from five to 12 hours a week," Johnson said. "It gives you a feel for working in other departments ... It's like building a resume."

Johnson has found the extra work through a new Walmart program called Access to Open Shifts, which lets workers sift the internal scheduling system for available slots. Launched as a pilot program at her Walmart store in Fort Smith, Ark., about a year ago, the system will be made available at the retailer's more than 4,000 U.S. stores by next week. As it has expanded in recent months, the program has helped part-timers work their way closer to full-time schedules.

Many of the Walmart employees who took part in walkouts and protests over the past two years have criticized the company for limiting hours and opportunities for part-timers. Workers at some stores even submitted petitions asking the company to stop cutting hours and to make more people eligible for full-time status.

The Access to Open Hours program appears to address that very critique, although a Walmart spokesman said it would be "inaccurate" to characterize the program as a response to any protests.

"Our associates are the best generators of ideas," said Kory Lundberg, the spokesman. "They've been telling us they want to know what opportunities are there in the store. This is one way to bring a little more transparency to the folks in the store to see what's available ... We're excited about where this can go."

Cynthia Murray, a 14-year employee who works at the Walmart store in Laurel, Md., and is a member of OUR Walmart, a labor-backed employee group, said, "We fought for this from the beginning."

"We were very adamant about it that workers were not getting enough hours," she said.

In some cases, the access to additional shifts can make a huge difference. Meiasha Bradley, a 26-year-old Walmart employee in Sacramento, Calif., told HuffPost that since her store launched the program last month she's managed to roughly double her hours. She called the rollout a "victory" for employees who demanded changes.

"A lot of the associates at our store and I know nationwide were going to management, saying, 'Hey our hours are getting cut, we need more,'" said Bradley, an OUR Walmart member. "I think that if we had given up we wouldn't have won this. We stood our ground."

"It will open up a lot of doors for our associates to become full-time," she added.

Last January, after a series of Black Friday strikes gained national attention, Walmart U.S. President Bill Simon announced that the company would make new efforts at bringing full-time work to employees who wanted it. As part of that, Simon said the world's largest private-sector employer would make its scheduling system more transparent to associates looking to pick up more hours.

In most stores, that used to mean speaking one-on-one with a manager about what shifts were vacant. But under the new system, employees can log onto Walmart's intranet system and immediately see what's available in different departments. The employees can then try to reserve it; if they're qualified, the shift is theirs.

It's a rare instance of retail workers reaping the benefit of technological advancements in scheduling. So-called just-in-time scheduling software has primarily helped retailers, rather than workers, by allowing them to determine precisely how many workers they'll need for how much time on a given day. Such fine-tuning has left a lot of these workers at the beck and call of managers, their schedules fluctuating and their hours rising and falling from week to week.

As the largest retailer in the world, Walmart has a way of setting trends in the industry, and it's possible other retailers will follow suit in adopting more open scheduling systems that better benefit workers.

In a sign of how well-received the scheduling program has been, even Dan Schlademan, director of Making Change @ Walmart, a campaign of the United Food and Commercial Workers union, has praise for the company's new system. The group has aggressively criticized Walmart for years over its pay and scheduling practices, and played a lead role in organizing the recent protests.

"There are people now who can work their schedules better. It's a great thing," Schlademan told The Huffington Post. "One of the number-one issues that workers have really been struggling with is hours."

Schlademan went on to say that the ongoing national discussion on low-wage work has often left out the question of scheduling. Pay and hours, he said, go "hand in hand."

"You can have the highest wage out there but without hours it doesn't mean anything," he said.

In recent years, workers across the retail industry have said that a lack of full-time hours has made it harder to make ends meet, particularly on wages that are generally low to begin with. The average retail salesperson earned $10.29 per hour, or $21,410 per year, in 2012. That's more than $2,000 below the federal poverty line for a family of four.

According to Walmart, the average wage for an hourly worker in its U.S. stores is $11.83 per hour. The company doesn't say how large its part-time workforce is, only that a majority of its workers are full-time.

Lundberg, the Walmart spokesman, said the new scheduling program will expose workers to more departments and potentially groom more of them for managerial roles. In Johnson's case, she's been able to pick up shifts as a cashier even though she's in the apparel department.

"I think every associate, if they can, should take advantage of it," she said.

Murray, the OUR Walmart member, said making more hours available is a step in the right direction, but she also said she wants to see more workers classified as full-time in order to receive benefits. Even if a worker brushes up against full-time hours on many weeks, if the worker is technically a part-timer, he or she doesn't enjoy the same health coverage, sick leave or other perks that full-timers do, Murray said.

"I think it's time that Walmart steps up and moves these part-time workers into full-time positions and gives them the benefits," she said.

The new scheduling system isn't the only change to come out of Walmart's human-resource department recently. Last month, the company revamped its policies for pregnant workers after employees and women's groups criticized them as inhospitable and perhaps even illegal. As The Washington Post reported over the weekend, the new guidelines should make it easier for pregnant workers to qualify for light duty.

Correction: The original post misspelled Johnson's first name.