Since the OP asked the question "when did he make, or even think about making the earth?" ... well, the first part isn't too hard. If we make a couple reasonable assumptions about the consistency of radioactive decay, then radiometric dating places the earth around 4.5 billion years old. However, I wouldn't presume to guess when the idea first popped into God's head.
Edited by Duh Puck, 18 February 2008 - 04:52 PM.