So the calulators that I see are just calculating odds then. I take it you could solve a block in your first 5 minutes if you were lucky enough. Or if unlucky then you might not solve one all month.

That's right. The calculators look at the current

odds per hash (this changes from time to time), and from that calculate the

average number of hashes it takes to solve a block. Then you can figure out the average time to solve a block based on your hash rate.