non negative values in difference between date columns in PowerQuery

You can basically use the same style when addiing column like this:

For Result1:

List.Max({	#duration(0,0,0,0),
		List.Min({[Cont Date 1],[Cont Date 2],[Cont Date 3]}) - [Other Date]
	})

And for Result2:

 List.Max({	#duration(0,0,0,0),
		List.Min({[Prop Date 1],[Prop Date 2],[Prop Date 3]})-List.Max({[Cont Date 1],[Cont Date 2],[Cont Date 3]})
	  })

You create lists as your "ranges" to choose from and then you can use List.Min or List.Max as the equivalent to MIN or MAX in Excel.

To create a list, you wrap your comma-separated elements into curly brackets: { FirstElement, SecondElement... }

Also you have to format the first 0 as a duration for the formula to work properly.

Not so elegant any more then:

= Table.AddColumn(#"Added Custom", "Custom.1", each try if List.Max({null,
		List.Min({[Prop Date 1],[Prop Date 2],[Prop Date 3]})-List.Max({[Cont Date 1],[Cont Date 2],[Cont Date 3]})
	  }) > #duration(0,0,0,0) then List.Max({null,
		List.Min({[Prop Date 1],[Prop Date 2],[Prop Date 3]})-List.Max({[Cont Date 1],[Cont Date 2],[Cont Date 3]})
	  }) else 0 otherwise null)