City history
Founded along the Río de la Plata in 1536, Buenos Aires transitioned from local solar time to standard time governed by its historical Naval Observatory and iconic British clock tower.
Chapter one
Earliest documented name
"Royal Settlement of Our Lady Saint Mary of the Fair Winds"
The earliest documented name was given in 1536 by Spanish conquistador Pedro de Mendoza in honor of the Virgin of Bonaria. Historical records do not document a specific indigenous Querandí place name for the settlement site.
Our Lady Saint Mary of the Fair Winds
First Spanish settlement founded by Pedro de Mendoza, abandoned five years later following armed resistance from indigenous Querandí communities.
City of the Most Holy Trinity and Port of Our Lady Saint Mary of the Fair Winds
Official name bestowed by Juan de Garay during the permanent second foundation of the city in 1580.
Fair Winds / Good Airs
Commonly shortened official name used throughout the 19th and 20th centuries after Argentine independence.
Autonomous City of Buenos Aires
Adopted following the 1994 Argentine constitutional reform that granted federal capital self-governing autonomous district status.
Chapter two
Argentina standardized national time on October 31, 1894, aligning federal offices and railways with the meridian of the Astronomical Observatory of Córdoba at UTC-4:17.
On May 1, 1920, Argentina joined the international hourly time zone system, setting standard time to UTC-4 and eliminating the previous fractional meridian difference.
Argentina introduced seasonal daylight saving time on October 15, 1931, advancing clocks by one hour to UTC-3 during summer to conserve fuel and electricity.
In October 1969, Argentina maintained summer daylight time year-round, establishing UTC-3 as the new baseline standard time offset for Buenos Aires.
Following temporary seasonal observations in 2007 and 2008, Argentina officially discontinued daylight saving time in 2009, remaining on year-round ART (UTC-3).
Chapter three
Spanish explorer Pedro de Mendoza established the initial fort of Santa María del Buen Ayre, which was destroyed and abandoned in 1541 due to indigenous resistance.
Juan de Garay refounded the city near Plaza de Mayo as Ciudad de la Santísima Trinidad, establishing a permanent Atlantic port city.
President Julio Argentino Roca created the Naval Observatory in Recoleta to determine exact astronomical time for ships navigating the port.
Buenos Aires inaugurated Line A of the Subte underground transit system, setting rapid transit schedules as the first subway in Latin America.
The British community presented a 60-meter clock tower in Retiro to commemorate the May Revolution centennial, featuring a Gillett & Johnston clock movement.
Presidential Decree 892 designated the Observatorio Naval Buenos Aires as the official national time authority, synchronizing public clocks and radio broadcasts.