I started clipping and filing by categories on trends as early as 1930 and my "youngest" file was started in 1945.
Span of time is important; the 3-legged stool of understanding is held up by history, languages, and mathematics. Equipped with these three you can learn anything you want to learn. But if you lack any one of them you are just another ignorant peasant with dung on your boots.

"The Happy Days Ahead" in Expanded Universe (1980)