Calculating Intervals Between Separate Rows of Data

Does it have to be DAX?  This can be solved quicker in Power Query.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("hdAxCsMwDAXQqxjPgVhfVtr6FNlNxq4ttPeHOKoFcYjTzV/o8YVz9uT84Ofn5/t+OX07GWkEHEkK4TDgMliG7NFDCInCYWCIL1BUZJlKs5K4I/hDoiiRbgvpJQ35tUzdFkrSENhhtx3hhqD+mmU2cj8h2FZ0YwOaxPYfvX1JqA01cgHLCg==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t, Person = _t, START = _t, END = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID", Int64.Type}, {"START", type datetime}, {"END", type datetime}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Person"}, {{"Rows", each _, type table [Index=nullable number, Person=nullable text, START=nullable datetime, END=nullable datetime]}}),
    idx = (tbl)=>Table.AddIndexColumn(tbl, "Index", 0, 1, Int64.Type),
    #"Added Index" = Table.AddColumn(#"Grouped Rows","Rows2",each idx([Rows])),
    diff = (tbl)=> Table.AddColumn(tbl, "Difference", each if [Index]=0 then null else if [START]- tbl{[Index]-1}[END] <= #duration(0,4,0,0) then [START]- tbl{[Index]-1}[END] else null),
    #"Added Custom" = Table.AddColumn(#"Added Index","Rows3",each diff([Rows2])),
    #"Removed Other Columns" = Table.SelectColumns(#"Added Custom",{"Rows3"}),
    #"Expanded Rows3" = Table.ExpandTableColumn(#"Removed Other Columns", "Rows3", {"ID", "Person", "START", "END","Difference"}, {"ID", "Person", "START", "END", "Difference"})

in
    #"Expanded Rows3"

How to use this code: Create a new Blank Query. Click on "Advanced Editor". Replace the code in the window with the code provided here. Click "Done".