Science and technology are upending how we learn. We separate the science from the snake oil and look at how parents, teachers, and policymakers respond.

The Indian city of Rajkot lies around 1,000 miles (1,600 km) due west of Kolkata, over in the Indian subcontinent’s easternmost corner. That’s a distance comparable to that between London, England, and Kiev, Ukraine, or between Atlanta, Georgia, and Denver, Colorado. But while London and Kiev, and Atlanta and Denver, are both two time zones apart, Kolkata and Rajkot observe a single time zone. All year round, their clocks say precisely the same time—even though their sunrises and sunsets are over an hour apart.

Since the mid-1950s, all of India has been in a single time zone. That’s despite the country’s huge land mass, spanning over 1,800 miles at its widest point, or 29 degrees longitude. (Worldwide, the general principle is a new zone every 15 degrees: Under British rule, India had three separate time zones, and sometimes even four.)

A new working paper (which has not yet been peer-reviewed or accepted for publication, but was recently featured on the Marginal Revolution economics blog) argues that India’s single time zone costs the country billions of dollar a year, and cheats children of the chance at a proper education.

It all comes down to bedtime, argues Cornell University PhD candidate Maulik Jagnani, who authored the paper: children wake up for school at roughly the same time throughout India, but go to bed later in places where the sun sets later. The result is that children growing up in western India get less sleep, which then shows up in lackluster performance in classes and test scores, and, eventually, lower wages than those growing up in the east. All that, because of a single time zone.

For each hour later that the sun sets in a given location relative to a second part of India, a child living in that first location will get 30 minutes less sleep. A child who lives somewhere where the sun sets at 7pm, for example, will, on average, get 30 minutes less sleep than a child who lives somewhere where the sun sets at 6pm. These children are then too tired to work effectively, Jagnani writes in the study: “Sleep-deprived students decrease study effort.”

Every additional hour of balmy afternoon sunlight is correlated with around 0.8 years less time spent in school, according to the study. “Children in geographic locations with later sunset are less likely to complete primary and middle school,” Jagnani writes. These effects continue as they age, he adds; living in places with later sunsets correlates with lower earnings.

As is often the case, the poorest children and families are hit hardest, with “low socioeconomic status” households least able to assert a hard bedtime in regions with later sunsets. Children of these families may lose an extra seven minutes per night compared to other children living in the same part of India. This might be because it’s just harder for them to practice good sleep hygiene—separate, indoor beds; mosquito nets; window shades; adequate nutrition—or because being poor is stressful, difficult, and time-consuming. If you’re worried about putting dinner on the table, being strict about your darlings’ bedtime may be the last thing on your mind.

India isn’t the only enormous country in the world to have a single time zone. China—roughly the same size as the continental US—is entirely on Beijing Standard Time. (In Urumqi, Xinjiang’s capital, the sun often sets around midnight.) There may be financial advantages to fewer time zones in a given country: As Quartz reporter Allison Schrager wrote for The Atlantic in 2013, the economic savings from better national coordination on time zones in the US could be enough to make up for a few lost hours of daylight—especially given that so many Americans spend their time indoors and in artificial light, anyway.

But though China may have a single time zone on paper, certain regions geographically and politically far from Beijing use an unofficial local time, imposing their own rules on the clock. As Matt Schiavenza wrote in The Atlantic, in response to Schrager’s piece, “In Xinjiang’s extreme west, near China’s border with Pakistan, Beijing Standard Time is so irrelevant that it isn’t even used on bus timetables.” Late last year, a Uighur man was detained by Chinese authorities for keeping his watch on this “unofficial” local time.

And if Jagnani’s right, a single time zone—at least in India—comes with a hefty price tag: His own back-of-the-envelope calculation suggests that India might incur “annual human capital gains of over $4.2 billion” by introducing one more time zone—as well as giving the country’s poorest children a better chance at a proper education.