Converting CSV date string to another format - powershell

Question

I got a CSV file with a date column with the format dd/MM/YYY HH:mm:ss, e.g. 14/11/2016 00:00:00.
I'm trying to batch convert the formating on that column to an ISO-8601 date format: YYYY-mm-dd HH:mm:ss
I have tried: ( I have edited I had an error on input string format...)
Import-Csv someCSV.csv | % {
$_.'[Date]' = ([datetime]::ParseExact(($_.'[Date]'),"dd/MM/YYYY HH:mm:ss").ToString('yyyy-MM-dd HH:mm:ss'))
} | Export-Csv 'C:\testBis.csv' -NoTypeInformation
I'm getting an error:
Cannot find an overload for "ParseExact" and the argument count: "2".
At line:1 char:69
+ ... Date]' ; ([datetime]::ParseExact(($_.'[Date]'),"dd/MM/YYY HH ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [], MethodException
+ FullyQualifiedErrorId : MethodCountCouldNotFindBest
I've had a look and tryed with Try parse and sever few ideas but nothing seam to work.
I dont know what I'm going wrong. any suggestions?

Answer 1

The pattern for matching the year must be yyyy (with lowercase y), there is no comma in your sample date, and you need to provide culture information for ParseExact(). I would also recommend to escape the forward slashes, otherwise they'll match whatever date separator is configured in the computer's regional settings. And you need to echo the modified record back to the pipeline, otherwise there'd be nothing to export.
$culture = [Globalization.CultureInfo]::InvariantCulture
Import-Csv someCSV.csv | ForEach-Object {
$_.'[Date]' = [DateTime]::ParseExact($_.'[Date]', 'dd\/MM\/yyyy HH:mm:ss', $culture).ToString('yyyy-MM-dd HH:mm:ss')
$_ # <-- feed modified record back into pipeline
} | Export-Csv 'C:\testBis.csv' -NoType

Answer 2

DateTime.ParseExact requires at least three parameters. The third parameter is the culture to use. You can pass the invariant culture [System.Globalization.CultureInfo]::InvariantCulture, eg:
([datetime]::ParseExact(($_.'[Date]'),"dd/MM/YYYY HH:mm:ss",[System.Globalization.CultureInfo]::InvariantCulture)
or a cleaner version:
$inv = [System.Globalization.CultureInfo]::InvariantCulture
$fmtFrom = "dd/MM/YYY HH:mm:ss"
$fmtTo = "yyyy-MM-dd HH:mm:ss"
Import-Csv someCSV.csv | % {
$_.'[Date]' = ([datetime]::ParseExact(($_.'[Date]'),$fmtFrom, $inv).ToString($fmtTo))
} | Export-Csv 'C:\testBis.csv' -NoTypeInformation
I removed the , from the format string because you mentioned that the actual format is dd/MM/YYY HH:mm:ss, not dd/MM/YYY, HH:mm:ss