Home Events - Diversity Atlas Guanacaste Day (Annexation of Nicoya Day) Date Jul 25 2024 Time All Day Guanacaste Day (Annexation of Nicoya Day) Guanacaste Day, also known as Annexation of Nicoya Day, marks the anniversary of Costa Rica’s annexation of the Guanacaste province in 1824. Share this event + Add to Google Calendar + iCal / Outlook export