From the U.S. Embassy in Panama:
Martyrs’ Day is a Panamanian holiday, which commemorates the January 9, 1964 riots over sovereignty of the Panama Canal Zone. The incident is considered to be a significant factor in the U.S. decision to transfer control of the Canal Zone to Panama through the 1977 Torrijos-Carter Treaties.
The U.S. Embassy in Panama City advises all U.S. citizens in Panama that Martyrs’ Day will be observed this year on Saturday, January 9, 2016. The U.S. Embassy alerts U.S. citizens to possible street closures and traffic congestion due to scheduled marches and other events around Panama City. All U.S. citizens are reminded of the sensitivity of this day and urged to remain diligent in your personal security.