jan 4, 1943 - Curt Herzstark designs Curta calculator
An Austrian engineer called Curt Herzstark was arrested by the Nazis in 1943 and while he was imprisoned at Buchenwald concentration camp for the duration of WWII, he worked on his design of a calculator featuring a modified version of Leibniz's "stepping drum" design. When the war finished, Herzstark made the smallest all-mechanical, four-function calculator built.
Added to timeline:
History of computing 30s - present day