1795day.year
The French First Republic adopts the kilogram and gram as its primary unit of mass.
In 1795, the French First Republic officially adopted the kilogram and gram as the primary units of mass, laying the foundation for the metric system.
In the aftermath of the French Revolution, the National Convention sought to standardize measurements across the nation in pursuit of rationality and fairness. On April 7, 1795, the French First Republic decreed the adoption of the kilogram and gram as the official units of mass. This reform abolished the myriad of local weight standards that had long hindered trade and science. The kilogram was defined based on the mass of a cubic decimeter of water, an innovative approach grounded in natural constants. The move marked a major milestone in the establishment of the metric system, which would later spread internationally. Standardized measures facilitated clearer communication in commerce, engineering, and scientific research. Today, the kilogram remains the base unit of mass in the International System of Units (SI), reflecting the enduring legacy of this revolutionary decree.
1795
French First Republic
kilogram
gram
1805day.year
Lewis and Clark Expedition: The Corps of Discovery breaks camp among the Mandan tribe and resumes its journey West along the Missouri River.
On April 7, 1805, the Lewis and Clark Expedition’s Corps of Discovery resumed its westward journey after wintering with the Mandan tribe along the Missouri River.
After an arduous winter spent among the Mandan people in present-day North Dakota, Meriwether Lewis and William Clark prepared to continue their famed expedition on April 7, 1805. The Corps of Discovery had built Fort Mandan to shelter 33 members of the team, forging crucial alliances with local Indigenous tribes. During their stay, the expedition members gathered supplies, repaired equipment, and documented flora, fauna, and native cultures. Their interactions with the Mandan provided vital knowledge of the terrain and river routes ahead. As spring arrived, the party set out along the Missouri River, charting its course towards the Pacific Ocean. This leg of the journey marked the beginning of their most challenging phase, as they navigated uncharted territories and harsh landscapes. The expedition’s scientific observations and maps would later become instrumental in America’s westward expansion and natural history scholarship.
1805
Lewis and Clark Expedition
Corps of Discovery
Mandan
Missouri River
1927day.year
AT&T engineer Herbert Ives transmits the first long-distance public television broadcast (from Washington, D.C., to New York City, displaying the image of Commerce Secretary Herbert Hoover).
In 1927, Herbert Ives achieved the first long-distance public television broadcast from Washington, D.C., to New York City.
Using mechanical scanning technology, AT&T engineer Herbert Ives transmitted moving images of Commerce Secretary Herbert Hoover. The broadcast traveled over telephone lines for over 200 miles. Viewers in New York saw a 48-line resolution image, a remarkable feat given the era’s technical limits. This demonstration marked a milestone in television history and paved the way for commercial TV. It showcased the potential of broadcast media to link distant audiences in real time.
1927
AT&T
Herbert Ives
television broadcast
Washington, D.C.
New York City
Commerce Secretary
Herbert Hoover
1948day.year
The World Health Organization is established by the United Nations.
The United Nations launches the World Health Organization to coordinate global public health efforts.
On April 7, 1948, the United Nations officially founded the World Health Organization (WHO) as its specialized agency for international public health. The WHO’s mandate included monitoring disease outbreaks, setting health standards, and supporting country-level healthcare systems. One of its first major successes was the global campaign to eradicate smallpox, achieved in 1980. Every year, April 7 is celebrated as World Health Day to raise awareness about pressing health issues. The organization has since expanded its work to include combating HIV/AIDS, malaria, and promoting universal health coverage. The WHO remains central to international efforts in improving health outcomes and responding to pandemics.
1948
World Health Organization
United Nations
1964day.year
IBM announces the System/360.
IBM unveils the groundbreaking System/360 mainframe family, standardizing computing architecture.
On April 7, 1964, IBM introduced the System/360, a revolutionary family of mainframe computers designed with a compatible architecture across different models. The System/360 line allowed businesses to upgrade performance without rewriting software, a major leap in computing flexibility. Its innovative use of integrated circuits and standardized instruction set influenced the entire computer industry. IBM invested over $5 billion in the development project, making it one of the largest corporate R&D efforts at the time. The launch transformed data processing in banking, government, and science. Many principles of System/360 architecture still underpin modern computing systems.
1964
IBM
System/360
1969day.year
The Internet's symbolic birth date: Publication of RFC 1.
The very first Request for Comments number 1 was published in 1969, marking the symbolic birth of the Internet.
In April 1969, the first Request for Comments (RFC 1) was published by Steve Crocker under the auspices of the ARPANET project.
RFCs became the formal documents for sharing protocols, procedures, and innovations among researchers.
This initial memo outlined methods for network host naming conventions, setting a precedent for future Internet standards.
Although simple by today’s standards, RFC 1 established a collaborative approach to network development.
The RFC series grew into the bedrock of Internet engineering, guiding the evolution of the global network.
This publication is celebrated as the symbolic milestone that launched the modern Internet era.
1969
Internet
RFC
1978day.year
Development of the neutron bomb is canceled by President Jimmy Carter.
President Jimmy Carter announced the cancellation of the controversial neutron bomb development project in 1978.
In 1978, President Jimmy Carter ordered the termination of the U.S. neutron bomb program, a tactical nuclear weapon designed to maximize lethal radiation while minimizing blast damage.
The decision came after fierce debate over the weapon’s moral and strategic implications.
Critics argued the neutron bomb would make nuclear war more thinkable by lowering civilian casualties from blast effects.
Supporters claimed it would improve NATO’s defensive capabilities in Europe against a Soviet advance.
Carter’s cancellation reflected his administration’s broader push for nuclear arms control and non-proliferation.
The move influenced subsequent U.S. and allied discussions on tactical nuclear weapons.
1978
neutron bomb
Jimmy Carter
1983day.year
During STS-6, astronauts Story Musgrave and Don Peterson perform the first Space Shuttle spacewalk.
Astronauts Story Musgrave and Don Peterson conducted the first-ever spacewalk from a Space Shuttle during the STS-6 mission in April 1983.
STS-6 was NASA’s sixth Space Shuttle mission and the first flight of Challenger. During this mission, Story Musgrave and Don Peterson performed history’s inaugural extravehicular activity from a shuttle. They tested new spacesuits and tools in the vacuum of space for nearly three hours. The spacewalk demonstrated critical capabilities for future construction and repair tasks in orbit. It also marked a major step toward assembling large structures on Space Station Freedom, the precursor to the International Space Station. Their successful EVA set safety protocols and suit performance standards that would guide NASA for decades.
1983
STS-6
Story Musgrave
Don Peterson
Space Shuttle
2001day.year
NASA launches the 2001 Mars Odyssey orbiter.
In April 2001, NASA launched the Mars Odyssey orbiter to map the Martian surface and search for signs of water.
Launched on April 7, 2001, Mars Odyssey was NASA’s longest-serving spacecraft at Mars. Its instruments included a thermal emission imaging system and a gamma-ray spectrometer. Odyssey quickly began mapping the planet’s mineral composition and detecting hydrogen-rich areas beneath the south polar ice cap. The orbiter also served as a relay station for other missions such as Mars Exploration Rovers Spirit and Opportunity. Discoveries of large subsurface water-ice deposits transformed our understanding of Mars’s climate history and habitability. Odyssey’s ongoing operation provided invaluable data for future exploration and landing site selection. It remains one of the most enduring successes in planetary science.
2001
NASA
2001 Mars Odyssey
2005day.year
First release of Git distributed version control system.
The first version of Git, a distributed version control system, was released on April 7, 2005.
Created by Linus Torvalds, Git was unveiled on April 7, 2005 to manage the growing Linux kernel project. Its distributed architecture allowed every developer to maintain a full copy of the repository, enhancing collaboration and resilience. Git emphasized speed, data integrity, and powerful branching and merging workflows. These innovations revolutionized how software teams collaborate and track changes. Over time, Git became the de facto standard for version control in open-source and commercial projects. Platforms like GitHub and GitLab further accelerated its adoption, making Git an integral tool in modern software development.
2005
Git
2011day.year
The Israel Defense Forces use their Iron Dome missile system to successfully intercept a BM-21 Grad launched from Gaza, marking the first short-range missile intercept ever.
Israel’s Iron Dome defense system achieved its first successful short-range missile intercept on April 7, 2011.
On April 7, 2011, the Israel Defense Forces recorded the first operational success of the Iron Dome missile defense system. A BM-21 Grad rocket launched from Gaza was detected and destroyed mid-air, proving the system’s effectiveness. Iron Dome’s advanced radar and Tamir interceptor missiles demonstrated high accuracy and rapid response. Developed to shield civilian areas from short-range threats, the technology represented a breakthrough in air defense. This success bolstered Israel’s strategic posture and inspired global interest in similar defense solutions. Since then, Iron Dome has intercepted thousands of rockets in subsequent conflicts, altering the dynamics of regional security.
2011
Israel Defense Forces
Iron Dome
BM-21 Grad
Gaza
short-range missile
2021day.year
COVID-19 pandemic: The Centers for Disease Control and Prevention announces that the SARS-CoV-2 Alpha variant has become the dominant strain of COVID-19 in the United States.
The CDC announced that the SARS-CoV-2 Alpha variant had become the dominant COVID-19 strain in the United States, marking a new phase of the pandemic.
On April 7, 2021, the U.S. Centers for Disease Control and Prevention reported that the Alpha variant of SARS-CoV-2, first identified in the United Kingdom, accounted for the majority of new COVID-19 cases. The Alpha variant was noted for its increased transmissibility compared to earlier strains. CDC scientists emphasized the importance of vaccination, mask-wearing, and social distancing to curb its spread. The announcement underscored the ongoing challenges of monitoring and responding to emerging variants during the global pandemic. Public health agencies intensified genomic surveillance and adjusted guidelines in response to the new dominant strain.
2021
Centers for Disease Control and Prevention
SARS-CoV-2 Alpha variant
COVID-19