(CNN) -- Ever since he was a boy, Friday has been a day of prayer and rest for Murad Alazzany.
Following a rhythm as old as Islam itself, Fridays meant lunchtime prayers at the mosque and relaxing with friends and family for the rest of the day.
But that was before protests and revolutions across the Middle East smashed decades-old regimes and caused unprecedented civil unrest.
Yemen's uprising started in January this year, spurred on by the Tunisian and Egyptian revolutions, and since then, Fridays have had a very different flavor for Alazzany and tens of thousands of Yemenis like him.
Alazzany, who is an assistant professor at Sanaa University, still goes to Friday prayers, known as Jumu'ah, but not in a mosque. Instead, he prays in the street alongside fellow activists and anti-government demonstrators.
And after prayers, they protest, arms punching the air, waving Yemeni flags, shouting slogans demanding change, while across town smaller numbers of pro-government supporters do the same but in favor of the regime.
"Fridays have turned into a big political event (in Yemen)," says Alazzany. "Friday prayers are events to show strength or support on the ground.
"People gather from the whole city -- and from the outskirts too -- to show solidarity with (the youth and opposition)," he adds.
The Muslim world's day of rest has long provided an opportunity to voice discontent in the Middle East.
As well as being a day off, all observant Muslims must congregate on a Friday for prayers.
As part of this, they listen to a sermon by an imam or sheikh -- a wise man respected in the community for his faith as well as his eloquence or logic. The sermons often cover social issues, politics and education, as well as religious themes.
"The mosque in Islam is not only a congregational temple for people to pray, but it is also a popular congress for people to meet once a week to discuss public affairs," explains Said Sadek, Professor of Political Sociology at The American University in Cairo.
Though Friday prayers are usually held in a mosque, they can be held in the street as long as there's a congregation and someone to lead the prayers.
That's what happened in Egypt on January 28 this year, the first Friday of the revolution, the so-called "Friday of Rage," when Tahrir Square became a huge, open-air congregational mosque for Friday prayers.
Revolutionary speakers addressed the crowd of anti-government demonstrators, who then protested in their hundreds of thousands while Mubarak's regime -- and the world -- looked on in disbelief.
Dr. Shadi Hamid of the Brookings Doha Center in Qatar, which researches socio-economic issues in the Muslim world, says that while Friday protests are not a new thing in the Middle East, the scale is unprecedented. He describes January 28, 2011 in Egypt as a "defining day."
"In many ways that was the turning point in the Arab Spring and in Egypt," he says. "That was the day the Egyptian revolution became the Egyptian revolution."
He adds that the success of the "Friday of Rage," helped by the use of social networking sites like Facebook and Twitter to mobilize masses, showed Egyptians the power of using Friday as a day of protest.
"Friday prayer is not just a site of prayer. It also has a symbolic power," he says.
"Prayer can also be a way of preparing to go to battle," Hamid continues. "Visually speaking, hundreds of thousands of people standing shoulder to shoulder is imposing and powerful. It gives the people who are praying strength."
Strategically, Fridays make sense too: People have a day off, so they can come to the protests, while organizers can devote their energies to organizing a big gathering that's likely to be successful.
"You can't hold mass protests every day of the week. That's going to sap your strength, that's unsustainable," Hamid says.
"So, it makes sense from a tactical point of view, from a strategic point of view, that you pick one day that everyone knows," he continues, "and everyone focuses their attention on that day."
The speakers invited to speak in Tahrir Square also set the tone of the Fridays. That's where the trend of naming Fridays came from, says Sadek.
"(The speakers) are usually gathered because of a public issue, a public topic," he explains. "That's why those Fridays were named the 'Friday of Victory,' the 'Friday of Purging,' the 'Friday of Justice.'"
"You can't have a 'Friday of Anger' every single Friday," Hamid adds. "It's a way of setting goals ahead of time."
The Egyptian revolution provided a template that activists in many other countries in the Middle East would emulate.
Now, Sadek says, the Friday protests have become so powerful across the region that there is a joke going around that Libyan leader Moammar Gadhafi would like to delete Friday from the week. "When Friday comes, the regimes in the Middle East are shaking," he adds.
While everyone agrees on the social, cultural and political significance of Friday protests in the Arab uprisings, the role of religion is a matter of dispute.
Sadek maintains that the majority of Egyptians who gathered on Fridays to protest during the revolution were "secular, urban, middle class intellectuals -- people who were not happy with the regime.
"Friday offered them an opportunity to meet with the people and make demands on the political system to respond," he says.
But Hamid says that the Tunisian and Egyptian revolutions and the uprisings in the rest of the region are "not secular."
"Liberals pray, leftists pray and Islam gives them strength too ... People care about their religion, they don't necessarily wear it on their sleeve, so in that way the Islamic component of these protests was almost implicit."
Alazzany puts it, perhaps, most succinctly: "It is in the mentality of Muslims that their faith and politics are not divorced."
CNN Arabic's Caroline Faraj contributed to this report.