Costa Rica runs at UTC-6 all year. Central Standard Time, no daylight saving. IANA identifier: America/Costa_Rica. San José is 6 hours behind UTC permanently, synchronized with parts of Mexico, Guatemala, Honduras, El Salvador, and Nicaragua (most of which also permanently use UTC-6 without DST).
Costa Rica tried daylight saving time in the mid-20th century, found it more trouble than it was worth at its latitude, and stopped.
The abolished military and the undisturbed clock
On December 1, 1948, Costa Rican President José Figueres Ferrer signed the new constitution and, in a theatrical gesture, handed the keys of a military barracks to the Minister of Education for conversion into a school. The army was abolished.
Costa Rica has not had a standing army since 1949, making it one of a small number of countries in the world that has constitutionally prohibited a military. The money that might have gone to military spending went instead to education and healthcare. Costa Rica now has the highest literacy rate and life expectancy in Central America.
The timezone kept ticking at UTC-6. No army was needed to defend it.
Biodiversity and the clock of seasons
Costa Rica contains approximately 5% of the world’s biodiversity in 0.03% of the world’s land area. The country has protected roughly 25% of its territory in national parks and reserves. This density of life includes 900 species of birds, 35,000 species of insects, and 12,000 plant species in a country the size of West Virginia.
Biological time here is exuberant: the breeding seasons of hundreds of species, the fruiting cycles of thousands of plant species, the migration routes of sea turtles and birds that pass through on schedules governed by temperature, daylight, and magnetic fields. The leatherback sea turtle arrives at Tortuguero Beach to nest from March to July. The quetzal’s breeding display peaks in the highland cloud forests from February to April.
UTC-6 is the civil administrative clock. The forest keeps its own calendar.
The coffee clock
Costa Rican coffee is among the world’s most regarded. The Central Valley’s volcanic soil and altitude (typically 1,200-1,800 meters) produce beans with the acidity, body, and flavor complexity that specialty roasters prize.
Coffee is a clock-dependent crop: flowering is triggered by the onset of the dry season, berries take roughly 9 months to develop from flower to ripe fruit, harvest runs from November through March (the dry season). The entire annual cycle is tied to seasonal variation.
At 10°N latitude, Costa Rica has modest but real seasonal variation. UTC-6, stable year-round, is the clock that morning coffee shipments to export terminals are timed to. The farm uses the seasons. The export infrastructure uses UTC-6.
