Acre Standard Time
UTC offset: −05:00
IANA identifier: America/Rio_Branco
Abbreviation: ACT
Observed in: State of Acre, Brazil
Population covered: approximately 900,000 (2022 IBGE estimate)
Acre Standard Time places clocks five hours behind Coordinated Universal Time. When it's 2:00 p.m. in Brasília, Acre reads noon. That two-hour gap inside a single country is wider than the time difference between London and Athens, and it has caused real headaches for travelers, federal administrators, and TV schedulers for decades. For the roughly 900,000 people who actually live in Acre, though, the offset matches what the sun is doing overhead.
The same offset applies uniformly across the state's 22 municipalities. There is no split, no partial observance, no odd county doing something different. From Rio Branco on the Acre River all the way to small river towns along the upper Juruá, every clock in the state agrees.
Why This Offset Exists Where It Does
Acre sits between 67 and 74 degrees west longitude. For reference, UTC−05:00 naturally corresponds to a band running from about 67.5 to 82.5 degrees west. So the offset isn't arbitrary. It's what you would pick if you wanted noon to roughly align with the sun's highest point. Eastern Standard Time in the United States covers a similar longitudinal range.
The state itself occupies the far northwestern corner of Brazil, wedged between Peru to the west, Bolivia to the south, and the enormous state of Amazonas wrapping around to the north and east. Rondônia touches it on the southeast. Nearly everything here sits within the Amazon Basin. Lowland tropical forest, river networks threading through dense canopy, seasonal flooding that reshapes what's passable and what isn't.
According to INPE, Brazil's National Institute for Space Research, around 87 percent of Acre's original forest cover was still standing as of 2023. That's high by Amazonian standards. Deforestation pressure does exist, particularly along the BR-364 highway corridor, but the overall preservation rate reflects decades of activism and the extractive reserve model that took root here in the late 1980s.
The 2008 Controversy
For most of its history as Brazilian territory (dating to the Treaty of Petrópolis in November 1903), Acre sat quietly at UTC−05:00. Nobody fought about it. The longitude justified it, and daily life worked.
Then came Federal Law 11.662, which took effect on June 24, 2008. Brazil's government decided to simplify the country's time zones, collapsing from four to three. Acre and the western portion of Amazonas state jumped forward one hour to UTC−04:00, aligning with Manaus.
On paper this was cleaner. In practice it was a mess.
Rio Branco sits at about 67.8 degrees west. Moving the clock forward an hour meant that for several months of the year, the sun did not rise until well past 7:00 a.m. by the clock. School started in darkness. Agricultural workers, and Acre still has plenty of them, lost their cool morning working hours. In the tropics the heat comes on fast, and losing that early window mattered.
People complained immediately. By 2010 the state legislature had passed a formal resolution asking Congress to reverse the decision. Congress did not move quickly. It took until 2013 for a statewide plebiscite to force the issue. The vote wasn't ambiguous. About 56 percent chose to return to UTC−05:00. Federal Law 12.876, signed October 30, 2013, made it official. Clocks went back on November 10 of that year.
What makes this unusual isn't just the reversal. It's that a popular vote drove the reversal. Federal time zone decisions in most countries are bureaucratic, decided by ministries or executive decree. Acre's residents essentially overruled the federal government through the ballot box. That's rare anywhere, and for a time zone matter specifically it may be unique in the Western Hemisphere.
Daylight Saving
Acre does not observe DST. Brazil discontinued the practice nationwide in 2019 via Decree 9.772, but Acre had already stopped participating long before that.
The reasoning is geographic. Between 7 and 11 degrees south latitude, day length varies by only 35 to 40 minutes across the entire year. There's essentially no long summer evening to exploit. A 2007 study commissioned by Brazil's Ministry of Mines and Energy looked specifically at equatorial states and found zero measurable electricity savings from DST. When you're that close to the equator, the concept simply doesn't accomplish anything.
Rio Branco
The capital. Population 419,452 in the 2022 IBGE census. It started in 1882 as a rubber-trading settlement perched on the banks of the Acre River, and it grew because rubber grew.
The name trips people up. Rio Branco translates to "White River" in Portuguese, which makes it sound like the city should be named after a waterway. It isn't. The city honors José Maria da Silva Paranhos Júnior, the Baron of Rio Branco, who served as Brazil's foreign minister and negotiated the annexation of Acre from Bolivia. The river running through town is the Acre River, not any Rio Branco.
Today Rio Branco is the state's commercial, administrative, and educational hub. The Federal University of Acre (UFAC) is here. So is the main airport connecting the state to the rest of Brazil. Most flights route through Brasília or Manaus. The city also serves as the primary access point for the Chico Mendes Extractive Reserve, which begins roughly 150 kilometers to the southeast.
Compared to other Brazilian state capitals, Rio Branco is small and isolated. Within Acre, though, it's the center of everything.
Cruzeiro do Sul
The state's second city, with about 89,760 residents. It sits on the Juruá River in the western Juruá Valley, and for a substantial part of each year, basically the entire wet season from December through March, you cannot drive there from Rio Branco.
The BR-364 extension that's supposed to connect the two cities has been under construction, on and off, since the 1990s. The section between Feijó and Cruzeiro do Sul still isn't paved through. When it rains heavily, the road becomes impassable. People fly, or they wait.
This isolation defines Cruzeiro do Sul's character. It functions as an independent economic hub for the surrounding indigenous territories and extractive communities of the upper Juruá basin. Goods flow along the river. Schedules depend on water levels as much as on what the clock says.
How ACT Compares to Nearby Offsets
Acre's UTC−05:00 places it in the same offset as Eastern Standard Time in the US and Canada. That alignment holds during the North American winter. In summer those regions spring forward to UTC−04:00, and the offset stops matching. Acre also matches Colombia, Ecuador, and Peru year-round, since none of those countries observe DST either.
Within Brazil, the closest offset is UTC−04:00 (Amazon Time), used by Amazonas, Roraima, Rondônia, and parts of Mato Grosso. The one-hour difference between Acre and neighboring Rondônia occasionally creates confusion for truckers on the BR-364 who cross the state line without realizing the clock just shifted.
Brasília, São Paulo, and Rio de Janeiro all run on UTC−03:00 (Brasília Time). That two-hour gap means when stock markets open at 10:00 a.m. in São Paulo, it's 8:00 a.m. in Rio Branco. Federal government offices in Brasília close at 6:00 p.m. their time, which is 4:00 p.m. in Acre. Anyone dealing with federal bureaucracy from the state has learned to account for that.
Daily Life on Acre Time
The clock matters less here than the river cycle. When water is high, transport shifts to boats and everything slows down. When it drops, roads reopen, trucks move, and commerce picks up pace.
June dominates the social calendar. The Festas Juninas, especially the Festa de São João, bring bonfires, forró music, quadrilha dancing, and food everywhere. Pamonha, canjica, pé-de-moleque. Acre's celebrations fold in indigenous and caboclo elements you won't find at the polished São Paulo versions.
November 17 is a state holiday, the anniversary of the Treaty of Petrópolis. Government offices shut down, and there are ceremonies in Rio Branco's central plaza. It's both a civic formality and a real point of identity. Acre didn't become Brazilian easily, and people remember that.
December 22 carries informal weight as well, marking the anniversary of Chico Mendes' assassination in Xapuri in 1988. Mendes was a rubber tapper and union organizer killed for opposing ranchers who were clearcutting forest. His death put Amazonian deforestation on the world stage and directly led to the creation of extractive reserves. The reserve named for him covers 970,570 hectares. About 10,000 people still live and work inside it, harvesting latex and Brazil nuts under the model Mendes fought for.
Technical References
In databases and software systems, Acre Standard Time appears as:
- America/Rio_Branco, the canonical IANA Time Zone Database entry
- ACT, the abbreviation used in Brazilian media and some older systems
- Horário do Acre, the informal Portuguese name
Before 2008, some implementations also referenced America/Eirunepe for the Juruá Valley portion of Amazonas state, which briefly shared UTC−05:00 with Acre before the Law 11.662 reshuffle pushed it to UTC−04:00.
Quick Reference
| Attribute | Value |
|---|---|
| UTC offset | −05:00 |
| DST observed | No |
| IANA zone | America/Rio_Branco |
| State area | 164,123 km² |
| State population | ~900,000 (2022) |
| Largest city | Rio Branco (419,452) |
| Forest cover | ~87% primary forest |
| State motto | "Nemo me tangit" (Let no one touch it) |
| Key state holiday | November 17 (Treaty of Petrópolis) |