Change random dates

Hi, 

In Power Query, Add a Custom Column and update [Column] to your actual Column name, 

if Value.Is([Column], type date)
or Value.Is([Column], type datetime)
then "INSTALL READY"
else if [Column] = null or [Column] = 0
then null
else Text.From([Column])

You can use the Table.ReplaceValue function, but you need to write custom M code in the Advanced Editor:

Source Data

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMtQ31TcyMDJVitWJVjIAk2DC0Ejf2BAkYwLmmugbmoN4FggVSIpN4YbEAgA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type any}}),
    
    #"Replace Dates" = Table.ReplaceValue(
        #"Changed Type",
        each [Date],
        "INSTALL READY",
        (x,y,z)=>if Value.Is(Date.From(y),type date) then z else y,
        {"Date"})
        
in
    #"Replace Dates"

Results