“Friday. Five o'clock in the afternoon. Maybe the hardest time to move unobserved through a city. Or, maybe the easiest. Because at five o'clock on a Friday nobody pays attention to anything. Except the road ahead.”

1890 - 1900

Opening remark made by Mattis in an address of 1st Reconnaissance Battalion Marines at Camp Pendleton in September 2002. As quoted by Nathaniel Fick, One Bullet Away: The Making of a Marine Officer (2005), p. 163.

Las heridas quemaban como soles
a las cinco de la tarde,
y el gentío rompía las ventanas
a las cinco de la tarde.
A las cinco de la tarde.
¡Ay qué terribles cinco de la tarde!
¡Eran las cinco en todos los relojes!
¡Eran las cinco en sombra de la tarde!
Llanto por Ignacio Sanchez Mejias (1935)

Fred Metcalf, The Penguin Dictionary of Modern Humorous Quotations (1987).

Often dated to 1943. Thorough research of Watson's writings and statements have produced no example of him saying this. It appears to be a corruption of a remark by Howard Aiken that four or five computers could meet all of the United Kingdom's computing needs. See Ralph Keyes (2006), The Quote Verifier.
Misattributed

Pt. 1, 8
Social Insurance and Allied Services (1942)
Context: Organisation of social insurance should be treated as one part only of a comprehensive policy of social progress. Social insurance fully developed may provide income security; it is an attack upon Want. But Want is one only of five giants on the road of reconstruction and in some ways the easiest to attack. The others are Disease, Ignorance, Squalor and Idleness.

Source: American on Purpose: The Improbable Adventures of an Unlikely Patriot

Source: The Gray Wolf Throne