Beginning July 1, maximum weekly working hours will decrease from 68 to 52 for companies employing 300 or more workers.

Though the related bill passed the National Assembly on Feb. 28, the government has yet to specify as to what should be regarded working hours, with just three weeks left to the enforcement date, causing confusion among companies.

Dong Seoul Bus Terminal in eastern Seoul posted a public notice Wednesday that it would stop selling bus tickets in advance online from July, then withdrew the notice after receiving a message from the Ministry of Land, Infrastructure and Transport. The terminal issued the notice because bus schedules for next month cannot be fixed due to the reduction in working hours.

Bus operators across the country estimate they need to hire up to 8,800 new drivers to maintain the current bus schedules under the revised rule, which requires them to cut weekly working hours to 68 from next month and 52 from July next year.

However, it is practically impossible to hire that many bus drivers at once.

When the 52-hour work week was approved by the parliament, its effect was foretold. The Korea Economic Research Institute estimated it would cost companies an additional 12.3 trillion won ($11.5 billion) a year to maintain their output. That‘s based on the idea of continued rates of pay. If employees lose their overtime pay with their overtime, the National Assembly Budget Office predicted those who work more than 52 hours a week will earn an average of 11.5 percent (or 377,000 won) less a month.

The government expects 140,000 to 180,000 jobs to be added, but most companies try to avoid hiring new workers by raising labor productivity.

According to the companies, working hours are relatively easy to count for factory or office workers, but that is not so for salespeople, field representatives or overseas workers.

It is not easy either to set working hours apart from time spent smoking, on break or dining together. There are no government-set guidelines on whether to regard as working hours such business-related activities as an after-work dinner with clients, a round of golf with customers, an employee workshop or travel for a business trip.

If the Ministry of Employment and Labor does not have its own criteria, even if unofficial, to discern working hours from nonworking hours, how can it tell if a company complies with the working hours or not?

So far, working hours have rarely aroused legal disputes, but from July, employers will be punished if they violate working hours, so court battles will be more likely.

As the ordinary wage has become an issue over which labor and management fight in court because it has not been clearly defined, working hours can experience a similar fate if the government leaves it up to each company to decide on them through collective bargaining.

The Labor Ministry should have issued guidelines on how to interpret working hours in details. It has yet to announce them or complementary steps after unveiling a plan last month to support companies if they hire new workers due to the shorter work week. It also remains mum about flexible working that companies want to utilize more broadly and variously to avoid side effects of the 52-hour work week.

Curtailing working hours is a campaign promise by President Moon Jae-in and also a key element of an income-led growth model he advocates, along with the minimum wage hike.

However, a cutback on working hours can become another headache to companies, especially if applied rigidly.

Of course, flexible work is important in making the shorter work week a success, but it is urgent to clear up confusion over the new rule.

Two years ago, the Anti-Corruption & Civil Rights Commission set guidelines on a law banning illicit solicitations, two months before it took effect. Nevertheless confusion and backlash could not be avoided in the early days of its enforcement.

If the shorter work week goes into force without meticulous preparations, controversy over its effects will be inevitable.