An innocuous tweet from a Malaysian minister last week has reignited a long-running debate about whether the Southeast Asian country is in the right time zone. 

In 1982, Peninsular Malaysia, the western part of the country, moved its clocks forward by 30 minutes to align its time zone with the states of Sabah and Sarawak on the island of Borneo.

The change, ordered by then-Prime Minister Mahathir Mohamad, was presented as a nation-building and modernizing move that would put the whole country on a single time.

But it also means that in Peninsular Malaysia the sun usually rises at around 7 a.m., roughly an hour later than in East Malaysia.

Some parents complain that they only have around 30 minutes of daylight before schools start at 7:30 a.m., and little time for children to eat breakfast or walk to school in daylight.

It also means that the sun sets relatively early, so many Malaysians are still at work or commuting when it is already dark and tend to eat long after sunset.

Reigniting the decades-old debate

Malaysian Minister of Investment, Trade and Industry Tengku Zafrul Aziz was visiting Sabah's capital, Kota Kinabalu, when, after one of his usual morning runs, he commented on social media about the joy of an early jog.

"Here, sunrise comes early, so I could start running at 6:00am before my first program at 8.30am this Sunday!" Aziz wrote on X.

What was supposed to be a jovial post about healthy living reignited the embers of a decades-old debate.

Many social media users have called on the government to move the clocks back an hour in Peninsular Malaysia, where the vast majority of the country's population lives.

Malaysian newspapers have published several articles on the question, and morning talk shows have invited experts to weigh in.

"I was recently in [Philippines' capital] Manila for a business trip, and it was nice to have a few hours of sunshine before heading into the office," Mohd Rahman, who works at a major bank in Kuala Lumpur, told DW.

Siti Abdullah, a mother of two in Georgetown, in northwest Malaysia, said that she had no idea about the science, but "a lot of people here think a change of time zone would be good for our health. It would certainly help with the school run."

Some medical experts DW spoke to said there is little solid scientific evidence to support those claims, although the topic has clearly become something of a national talking point.

It even reached parliament last year, although then-Minister of Investment, Trade and Industry Liew Chin Tong replied that any time zone change would have a "significant impact on the economy" and said that the government was not considering a change.

A history of shifting clocks

Both Singapore and Malaysia were forced to switch to GMT+9 during World War II at the orders of their Japanese occupiers, who wanted the region to follow Tokyo time.

After the war, Peninsular Malaysia adopted UTC+7:30, a halfway point between its earlier time and the wartime clocks, before moving again to GMT+8 on January 1, 1982.

This leaves Kuala Lumpur, the Malaysian capital, in an unusual position. It sits at a similar longitude to Thailand's capital Bangkok and Indonesia's capital Jakarta, yet operates an hour ahead of both cities. At the same time, it shares a time zone with Manila, the Philippine capital, which lies about 2,500 kilometers to the east.

Singapore, at the southern tip of Peninsular Malaysia, followed Kuala Lumpur's lead in 1982 and also moved to GMT+8 to "avoid inconvenience to businessmen and travelers," according to its government at the time.

According to some critics, the lack of early-morning sun and an early sunset disrupts Malaysians' circadian rhythms, the 24-hour cycle of physical, mental and behavioral changes regulated by light and darkness.

However, experts are skeptical.

Mahadir Ahmad, a senior lecturer and clinical psychologist at the National University of Malaysia, told DW that he is not convinced a one-hour difference is significant enough to cause widespread health problems, noting that there is no strong evidence from regional studies to support that claim.

"What is more important is to maintain the sleep-wake cycle (circadian rhythm), and as long as our sleep routine does not suppress melatonin production, we could go to sleep and wake up based on the daytime and nighttime cycle," he said.

"The existing evidence shows that sleep deprivation and circadian misalignment could cause cognitive performance and mood disturbances," he added.

Nurul Aqilah Hasan Ashaari, a clinical dietitian, pointed out that several other Southeast Asian countries that follow a "right" time zone have worse health indicators than Malaysia, and that social behaviors such as diet, exercise, and working hours are far more important than the precise time the sun rises or sets.

For now, scientists say, Malaysia's health challenges appear to be driven more by lifestyle than by its position on the world time zone map.

One ASEAN time?

In parallel, there is a similarly loud chorus of calls for Malaysia to stay on GMT+8 but for the rest of Southeast Asia to follow suit, albeit for economic rather than health reasons.

In January, Abdul Wahid Omar, the chairman of Bursa Malaysia, the country's stock exchange, argued that the entire Association of  Southeast Asian Nations (ASEAN) region should adopt a common time zone, which, conveniently for Malaysia, he said ought to be GMT+8.

This would "further integrate ASEAN as a compelling economic bloc" and align the region with China, Hong Kong and Taiwan, he told a business forum earlier this year.

Singapore, which is also on GMT+8, has publicly backed this idea. It was first mooted by the city-state's then-premier, Goh Chok Tong, in 1995, resurfaced in 2006, and again in 2015, when Malaysia last held the ASEAN chairmanship.

Adopting a single time zone would require major changes. Thailand, Cambodia, Laos and Vietnam would have to move from GMT+7, although Bangkok and Hanoi have floated the idea in the past.

Myanmar, currently on GMT+6:30, would have to move its clocks forward by an hour and a half.

Indonesia would face the biggest challenge. The vast archipelago spans three time zones — GMT+7, GMT+8 and GMT+9, although the island of Java, where most of its major cities are located, adheres to GMT+7.

There have been on-and-off discussions since 2012 about unifying the country under a single GMT+8 time zone, but the proposal has repeatedly been postponed and never implemented.

For now, Southeast Asia remains almost evenly split between GMT+7 and GMT+8, with Peninsular Malaysia and Singapore the outliers.

Whether a minister's enjoyment of a morning run is enough to shift the region's clocks remains an open question.

Edited by: Srinivas Mazumdaru