TIme Interval Calculation

Here's one way:

  (Paste the code below into the Advanced Editor and explore the Applied Steps to understand.

   Then adapt to your actual data)

• Group by LocationCode
• Sort the subgroups (might not be necessary)
• Add an Index column to each subgroup to enable 
  
  • Subtract each time stamp from the next one, UNLESS it is the first (Index = 0)
• Expand the subtable

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQyNtE1MlHSUTLRNwIiAyNTBUMDKwMDhcRcpVgdHAoMMRSYQhSYQhWA5AtwyxsjyZuYmpljdUEiXnkTUwU8CowwLEB1gAW6+ajSllDpWAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [LocationCode = _t, #"Date-Time-Stamp" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"LocationCode", type text}, {"Date-Time-Stamp", type datetime}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"LocationCode"}, {
        {"Intervals", (t)=>
            [a=Table.Sort(t, each [#"Date-Time-Stamp"]), //Sort may not be necessary
             b=Table.AddIndexColumn(a,"Index",0,1,Int64.Type),
             c=Table.AddColumn(b,"TimeInterval-Minutes", each 
                    if [Index] = 0 then null else Duration.TotalMinutes([#"Date-Time-Stamp"] - b[#"Date-Time-Stamp"]{[Index]-1})  )
            ][c], 
        type table [LocationCode=nullable text, #"Date-Time-Stamp"=nullable datetime, #"TimeInterval-Minutes"=Int64.Type]}}),
    
    #"Expanded Intervals" = Table.ExpandTableColumn(#"Grouped Rows", "Intervals",
                                {"Date-Time-Stamp", "TimeInterval-Minutes"})
in
    #"Expanded Intervals"

Source

Results