DATEDIFF DAX

Power BI does not think like Excel.  Unpivot your data  to these columns

Name

Contact

let
    Source = #table(null,{{ "James ", "1/1/2026 01:30:00 ", "1/15/2026 01:30:00 ", "1/17/2026 01:30:00 ", "1/19/2026 01:30:00 "},
{ "Anthony ",  "1/17/2026 01:30:00 ", "1/19/2026 01:30:00 ", "1/21/2026 01:30:00 ", "1/22/2026 01:30:00 "},
{ "Okito ",  "1/17/2026 01:02:00 ", "1/16/2026 01:30:00 ", "1/22/2026 01:30:00 ", "1/31/2026 01:30:00 "}}),
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(Source, {"Column1"}, "Attribute", "Contact"),
    #"Removed Other Columns" = Table.SelectColumns(#"Unpivoted Other Columns",{"Column1", "Contact"}),
    #"Renamed Columns" = Table.RenameColumns(#"Removed Other Columns",{{"Column1", "Name"}}),
    #"Changed Type" = Table.TransformColumnTypes(#"Renamed Columns",{{"Name", type text}, {"Contact", type datetime}})
in
    #"Changed Type"

That way the number of contacts for each name can be flexible.

Then you can run the standard math functions against your data, including min and max difference between values

To compare any two names you would use measures that can modify the filter context, or visual calculations.

Oftentimes a visual solution may be easier.

What is your expected outcome based on the sample data you provided?