The world basically stops when the See of Peter goes vacant. You’ve seen the images: the massive crowds in St. Peter’s Square, the somber bells, and that tiny chimney perched on the Sistine Chapel roof. But the big question everyone asks while the Vatican is in "Sede Vacante" (the empty seat) is simple: When does the conclave begin for the new pope?
Honestly, it’s not just a random date picked out of a hat. It’s a mix of ancient tradition and very strict modern laws that keep the whole thing from turning into a chaotic free-for-all.
The 15-to-20 Day Rule
If you’re looking for a hard date the second a pope passes away or resigns, you won't find one. That’s because the "General Congregations"—the daily meetings of the cardinals—have to actually vote on the start date.
According to the Apostolic Constitution Universi Dominici Gregis (the big rulebook written by John Paul II and tweaked by Benedict XVI), the conclave must start no earlier than 15 days and no later than 20 days after the papacy becomes vacant.
Why the wait? It’s practical.
- Cardinals are scattered across the globe. Some are in remote parts of Africa, Asia, or South America. They need time to pack a bag and get to Rome.
- The Novemdiales. This is the nine-day official mourning period. You can’t exactly jump into a high-stakes election while the previous pope's funeral rites are still ongoing.
- The "General Congregations." Before they lock themselves in, the cardinals meet daily to talk about the state of the Church. They’re basically interviewing each other without calling it an interview.
The 2025 Precedent: A Real-World Timeline
We saw this play out in vivid detail during the most recent transition. When Pope Francis passed away on April 21, 2025, the clock started ticking immediately. It wasn't a guessing game for long. By April 28, during their fifth meeting, the College of Cardinals officially set the date.
The conclave began on May 7, 2025.
That was exactly 16 days after the vacancy began. It fit perfectly within that 15-to-20 day window. If they had tried to start on May 2, it would have been illegal under church law unless every single voting cardinal was already in Rome and they voted to waive the wait. Benedict XVI actually made it possible to start earlier if everyone is present, but usually, they take the full 15 days to breathe and deliberate.
Who actually gets to walk through those doors?
Not every guy in a red hat gets a vote. It’s a bit of a "sorry, you’re too old" situation. Only cardinals who haven't hit their 80th birthday by the day the pope dies (or resigns) can enter the Sistine Chapel.
In the 2025 conclave, we had a record 133 cardinal-electors. That’s a lot of people to cram into the Domus Sanctae Marthae, which is the hotel-like building where they stay so they don't have to sleep on cots in the chapel like they did in the old days.
The Day the Conclave Starts
The actual "Day One" is a marathon. It doesn't just start with a vote.
In the morning, the cardinals head to St. Peter’s Basilica for the Missa pro eligendo Pontifice—the Mass for the election of a pope. It’s public. Anyone can go. Then, in the afternoon, the real secrecy kicks in. They process into the Sistine Chapel singing the Veni Creator Spiritus, calling on the Holy Spirit to basically not let them mess this up.
Then comes the coolest part of the whole ritual: Extra omnes.
The Master of Papal Liturgical Celebrations (it was Archbishop Diego Ravelli in 2025) stands at the doors and yells "Extra omnes!" which means "Everybody out!" If you aren't a voting cardinal, you’re gone. The doors are locked. The windows are sealed. The Swiss Guard stands watch.
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What Happens Behind the Locked Doors?
Once they’re in, the schedule is grueling. They usually do one vote on that first afternoon. If nobody gets a two-thirds majority (which almost never happens on the first try), we see the black smoke.
After that first day, it’s usually four votes a day:
- Two in the morning.
- Two in the afternoon.
If they go three days without a winner, they take a break for 24 hours. No voting. Just prayer and probably a lot of coffee and quiet arguing. In 2025, the world watched as names like Cardinal Pietro Parolin and Cardinal Robert Prevost were discussed. When American Cardinal Robert Prevost was eventually elected, the white smoke finally signaled the end of the wait.
Actionable Insights for Following the Next Conclave
If you're tracking the next time the "When does the conclave begin" question pops up, keep these markers on your calendar:
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- Day 0: The vacancy begins (death or resignation).
- Days 1-5: Cardinals arrive in Rome and begin General Congregations.
- Day 4-6: The funeral of the deceased pope usually occurs here.
- Days 1-9: The Novemdiales (mourning period).
- Day 15-20: This is your "Conclave Window." Watch for the official announcement around Day 7 or 8.
Don't listen to rumors about "emergency elections" starting in three days. The Vatican moves slowly on purpose. The law is designed to prevent a "snap election" where the people already in Rome could seize power before the cardinals from the other side of the world can land their planes.
If you want to stay ahead of the news, follow the official Vatican Press Office bulletins or the Sala Stampa. They are the only ones who will give the definitive time for the "Extra omnes" command. Once those doors shut, the only way we know what's happening is by watching the color of the smoke.
Make sure you're looking at the right chimney; in 2025, thousands of people were staring at the wrong roof for twenty minutes before someone pointed them toward the Sistine Chapel. Use a reliable live stream that has a fixed camera on the actual flue to avoid the "fake smoke" scares that always happen on social media.