calculate with date

Hi Nelleke-NL 

You can create a custom cloumn and input the following code

=if [Einddatum]<>null then Number.Round(Number.From(([Einddatum] -[Startdatum])/( 365.25 / 12 )),0) else Number.Round(Number.From((DateTime.Date(DateTime.LocalNow()) -[Startdatum])/( 365.25 / 12 )),0)

Output

and you can create a blank query and put the whole code in advanced editor in power query

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("fZNJjsQgDEWv0mIdJGxCgLNEdf9rtIcQPqirF5E8vHj4wH2HGilyYg5HIPnA7W7m8DnuUGZcP3DFcFMx4pnImgSf+rB38txITvEEMs9MURJnOWMD8pyZayO37kBWzYJPVyyT5Bov8Ui3adoRfOmuc1J3MoF2mqUvIi2J9C+JY5F3nLtfuBHjrmtajiLWeZQLmTeSOWYo2gDVU8KAzFL+VpTKJinXRXzpZ24ytV3yGdEdH8foIYhgFQU6ws/obLdF9aHmnd8A56cYOVt9PWO7lYTAa+NCNlKChVb7Qd+ZvBIExAZFqQFqaQj0r2TeSBGsAkrjvah6dldmYNp2ohmqFhcIArFD1TGN3hB9peAn/0ku1OcX", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Gemaakt op" = _t, Dossiernummer = _t, Startdatum = _t, Einddatum = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Gemaakt op", type text}, {"Dossiernummer", Int64.Type}, {"Startdatum", type text}, {"Einddatum", type text}}),
    #"Changed Type with Locale" = Table.TransformColumnTypes(#"Changed Type", {{"Gemaakt op", type date}, {"Startdatum", type date}, {"Einddatum", type date}}, "en-GB"),
    #"Added Custom" = Table.AddColumn(#"Changed Type with Locale", "Custom", each if [Einddatum]<>null then Number.Round(Number.From(([Einddatum] -[Startdatum])/( 365.25 / 12 )),0) else Number.Round(Number.From((DateTime.Date(DateTime.LocalNow()) -[Startdatum])/( 365.25 / 12 )),0))
in
    #"Added Custom"

Best Regards!

Yolo Zhu

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