Past obviously. Sell your house in present, go back to the 1800's, put all in a SAFE, SECURE back (To avoid depression) And in the present it would be worth a hell of alot more. Or I would go back and take the idea of say, Microsoft, invent it in my name, and then when I go to the present be as rich as Bill Gates. Then when I am rich as Bill Gates, use money to build time machine, go back in time, stop 9/11.