Duration Conversion and Calculation

You might be getting this error becuase you are already automatically converting the data to a time, and then trying to make a duration from that.

If you have an automatic step that is converting the column to a "time", delete that step and replace it with a step that converts it to duration.

This gives an error:

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQwMFDSUTIwtjIwsjI2UIqNBQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Contact_ID = _t, TMA = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"TMA", type time}}),
#"Changed Type1" = Table.TransformColumnTypes(#"Changed Type",{{"TMA", type duration}})
in
#"Changed Type1"

This works ok:

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQwMFDSUTIwtjIwsjI2UIqNBQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Contact_ID = _t, TMA = _t]),
#"Changed Type1" = Table.TransformColumnTypes(#"Source",{{"TMA", type duration}}) // note removed step from previous example
in
#"Changed Type1"

Hope this helps,

Peter