Notable ideas around 400CE:
Explanation of lunar eclipse and solar eclipse, rotation of Earth on its axis, reflection of light by moon, sinusoidal functions, solution of single variable quadratic equation, value of π correct to 4 decimal places, diameter of Earth, calculation of the length of sidereal year
Influenced
What's really frustrating is that Bourbaki's way of approaching set theory and abstract algebra remains canon today. As a result, even though category theory and modern mathematical logic are nearing their first centennials, folks are still very hostile towards any reorganization of fundamental objects which doesn't place sets on the bottom as the bedrock.
That is a trivialization of what was at the time a great leap forward. War had shattered the old schools which had promoted the idea that each application had special methods and formulae which were fundamentally different from and incompatible with each other. The idea that people from radically different fields were all making similar use of the same concepts and could instead make use of the same robustly generalized concepts and formulae was so radical that it was necessary to hide behind a psuedonym because so many professionals felt their careers were put at risk by these meddlesome mathematicians. Nicholas Bourbaki took the mathematics of the time from something resembling magic incantations into the modern world of reasoning from base principles.
Notable ideas around 400CE: Explanation of lunar eclipse and solar eclipse, rotation of Earth on its axis, reflection of light by moon, sinusoidal functions, solution of single variable quadratic equation, value of π correct to 4 decimal places, diameter of Earth, calculation of the length of sidereal year Influenced