In addition, companies are allowed to delay paying employees for the extra hours by up to three years.
Is there anything else angering protesters?
Yes. The same day a new law passed that will see the setting-up of administrative courts overseen directly by the justice minister.
Critics say it will allow political interference in judicial matters and further undermine the rule of law.
How did opposition MPs react?
Opposition MPs tried to block Wednesday's vote for the amendment to the "slave law" and the new judicial legislation.
One MP from the far-right Jobbik party even marched to the president's office to call on him not to sign the amendment.
Other politicians went to a protest behind the headquarters of Prime Minister Viktor Orban's Fidesz party, before returning to Kossuth Square, in front of the parliament.
The parliament demonstration later saw fights break out between the protesters and the police, who used tear gas and pepper spray.
What has happened since?
Since last Wednesday (December 12), there have been several further protests: on Thursday, Friday, Sunday, Monday and Tuesday.
The largest was on Sunday (see above) when, after marching from Heroes Square to the parliament, people walked to the headquarters of the public media broadcaster (MTVA).
Some opposition MP's entered the building and tried to read their five-point petition, which you can peruse below:
Protests outside Hungary
Demonstrations in at least 30 foreign cities were organised in the wake of the adoption of the amendment to the law.
The largest took place in the Austrian capital of Vienna on Wednesday with more than 350 people turning out.
A new Facebook group called Coming Home To Work Overtime facilitated many of the acts, garnering 4,300 members in a week.
The group's creator called on members to exchange information with Hungarian friends living abroad about the demonstrations within the country's borders.
Several European capitals have also seen action, including Paris, Brussels, London, Warsaw, Bern, Berlin, The Hague, Stockholm, Dublin, Copenhagen, Reykjavik and Lisbon.
In addition, protests sprang up in some German cities — Stuttgart, Bremen, Munich, Linz — as well as in Edinburgh and Bournemouth in the UK.
Further away from Hungary in Toronto, Canada, and Melbourne, Australia, opposition to the amendment was also felt.
There was also sympathy for the movement in the Israeli capital.
What happened next?
On Monday morning security guards forcibly-removed two opposition MPs from the building of the public broadcaster.
MTVA said in a statement that it had filed a complaint with police after the MPs allegedly repeatedly ignored warnings from security about entering blocked areas, harassed employees and tried to blackmail the broadcaster.
"In the morning, the lawmakers again tried to enter the work areas," the statement read. "They regularly harassed the staff of MTVA, and they chased the workers along the corridors to work."
But the MPs hit back.
One of them, Bernadett Szél, said: "We were surrounded by a lot of armed security staff members, I identified four different security agencies, but we could not speak with any of the directors or editors of the state media.
"We tried to find some editors in the offices but they did not let us enter. When we wanted to go to the offices upstairs, they told us that the stairs are slippery."
Another, Ákos Hadházy, said: "Everything has been unveiled here by these actions, but this is just the beginning, we have lots to do to tear down this bastion.
"Unfortunately, the state media is the symbol of the filthy and mean government propaganda and the disinformation dictatorship which had been created by the government."
Is this like the 'gilets jaunes' ('yellow vests') in France?
Even though the Hungarian protesters on the streets of Budapest received some support on the internet from French people, what is happening in Hungary is not the same as the "yellow vests" movement in France.
People on the streets are waving EU flags and one of their demands is that Hungary should join the European Public Prosecutor's Office and they say that they are fed up with the public media, spreading fake news mostly about migrants.
The new element of these protests, compared to others in 2010, is that opposition parties are united and protesting together.
Government party politicians claim the amendment is letting people work more extra hours and it is in their interest.
But unions are not sharing this opinion and they are protesting with people on the streets.
Hungarian Prime Minister Viktor Orbán said to the media after the vote on Wednesday that the law is good and important.
In an interview with Euronews, government spokesman Zoltan Kovacs hit out at western media reporting of the protests.
He said the demonstrations had been organised by a "weak opposition" and refuted claims it did not have a fair voice.