Want to add date to SQL results as static column, in Powershell

so I have the following powershell script, the script works however i would like to add a column to the front of the table that is simply 'date' and every line would have '$dMonth' in the beginning of the csv.

$dMonth= (Get-Date).AddMonths(-0).ToString("dd-MM-yyyy")
$DBServer = "cdiserv1"
$databasename = "SUBSCRIBER"
$Connection = new-object system.data.sqlclient.sqlconnection
$Connection.ConnectionString ="server=$DBServer;database=$databasename;trusted_connection=True"

$SqlCmd = New-Object System.Data.SqlClient.SqlCommand

$SqlQuery = @"
SELECT  isnull(B.AcctLineCode, '') AS OLC,
        isnull(B.AcctNum, '') AS OAN,
        isnull(A.AcctLineCode, '') as NLC,
        isnull(A.AcctNum, '') AS NAN,
        isnull(B.Name, '') AS ONA,
        isnull(A.Name, '') as NNA,
        isnull(B.UserField1, '') AS O1,
        isnull(B.UserField2, '') AS O2,
        isnull(B.UserField3, '') AS O3,
        isnull(A.UserField1, '') AS N1,
        isnull(A.UserField2, '') AS N2,
        isnull(A.UserField3, '') AS N3,
        case when A.AcctNum != B.AcctNum or A.AcctLineCode != B.AcctLineCode then 'ACCOUNT MOVED'
        when A.Name != B.Name then 'NAME CHANGE'
        when A.UserField1 != B.UserField1 OR A.UserField2 != B.UserField2 OR A.UserField3 != B.UserField3 then 'FEATURE CHANGE'
        when A.AccountID is not null and B.AccountID is null then 'ADDED ACCOUNT' 
        when A.AccountID is null and B.AccountID is not null then 'DEELETED ACCOUNT' end [Result]
FROM    [CDISERV1].[SUBSCRIBER].[dbo].[Subscriber Data] A
        FULL OUTER JOIN [CDISERV2].[SUBSCRIBER].[dbo].[Subscriber Data] B ON A.AccountID = B.AccountID
WHERE (A.AccountID is not null and B.AccountID is null)
OR (A.AccountID is null and B.AccountID is not null)
OR A.AcctLineCode != B.AcctLineCode
OR A.AcctNum != B.AcctNum
OR A.Name != B.Name
OR A.UserField1 != B.UserField1
OR A.UserField2 != B.UserField2
OR A.UserField3 != B.UserField3
"@
    
$Connection.open()
$SqlCmd.CommandText = $SqlQuery
$SqlAdapter = New-Object System.Data.SqlClient.SqlDataAdapter
$SqlAdapter.SelectCommand = $SqlCmd
$SqlCmd.Connection = $Connection
$dt = New-Object System.Data.DataTable
$SqlAdapter.Fill($dt) | Out-Null
$Connection.Close()
$dt | Export-Csv -Path Z:\OP\CSV\AIS$dMonth.CSV -force -NoTypeInformation

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i really wanted to have the script merge into a single file, as i run this script every evening just before midnight, if it would append the date would show when the data was extrapolated essentially as a log, i have discovered sadly this is not possible for Export-Csv with the version of powershell i am using so i merge the files after exporting.

my desired results would look like the following...
"date","OLC","OAN","NLC","NAN","ONA","NNA","O1","O2","O3","N1","N2","N3","Result"
"15-05-2018","xxx","1234","xxx","1233","na","na","c7","n3","b5"," "," "," ","ACCOUNT MOVED"