Spain's celebrated siesta could be facing a modern makeover.

Political parties are promising to turn the clock back in Spain and eliminate a time quirk dating from World War II, a move that could radically change Spaniards' eating and sleeping habits.

Until the 1940s, Spain was on the same Greenwich Mean Time as Britain and Portugal, being in roughly the same longitude. But during World War II, Spain, Britain and some other countries added on an hour, going on the same time as Nazi Germany to maximize factory productivity so people could get home before blackouts.

While Britain reverted back after the war, Spain, under the dictatorship of Gen. Francisco Franco, never did. That led to almost everything being done an hour or more later in Spain than was natural.

Job hours vary greatly, but many Spaniards start work at 10 and finish at 8 p.m. Lunch is generally around 3 p.m. while dinner can start at 10 p.m. or later, leading often to late nights and less sleep.

Now acting Prime Minister Mariano Rajoy says if he manages to form another government following the Dec. 20 inconclusive election he will push for a new work-life balance law that would switch Spain back to its original time zone.

The law would include a working day that ends at 6 p.m., thus scrapping the country's lengthy lunch-hour breaks that some use to grab a siesta.

"We cannot lose contact with Europe. The rationalization of the timetables of work shifts and government institutions is of capital importance," Rajoy said.

Nuria Chinchilla, an IESE business school professor who worked on a study urging the change in 2013, said the move would benefit both businesses and people. The study found that being ahead an hour meant Spaniards slept an hour less than recommended, which had a negative effect on productivity, absenteeism, stress, accidents and school drop-out rates.

"We have not been in our time zone for more than 70 years," she said.

Some say the measure could end the siesta but Chinchilla disagreed.

"The siesta is not a reality anymore," she says. "This was in agricultural times and before the Civil War too ... (but not) in Barcelona or Madrid, where for sure nobody is going back home to have lunch."

Still, many Spaniards take siestas during the sweltering hot summer holidays or on weekends if they can.

Rajoy's proposal mirrors one by two other parties also looking to form the next Spanish government, the Socialists and the Ciudadanos party. But no party has been able to muster enough parliamentary support to do that — making a new vote look more likely day by day.

That means no time-change laws in the near future — and Spaniards can still sneak off for a siesta as the weather gets warmer this year.