Much longer than that, and was available way before an internet. I graduated STEM high school in St. Petersburg in 1981, and I had several classmates who were big funs of chemistry. That they were able to create from textbooks, school lab ingredients, and understanding:

WWI era poison gas, tear gas, potassium cyanide, and bunch of explosives like acetone peroxide.

LLMs have all of that knowledge in training data