All results of command jobs containing show commands get stored in the database, the Diff node config tool gives you an overview of these results.

Put in the nodename in question and click the Get Commands button.

The available show commands stored will be listed, select the desired one and click the Get Revisions button.

Whereupon the dates of the beforehand selected commands will be shown, select the dates you want to compare: output will be shown underneath after clicking the Show differences button.