First I call all iterations that I have in my project – and it works fine and then I want to create a new one via the API. , but the method doesn’t work, I get the error:

The remote server returned an error: (400) Invalid request.

Is there an issue with this not really working properly or am I doing something wrong?

# *the Powershell code:*

# Variables
$organization = "x"
$project = "y"
$pat = "z"

$baseUrl = "https://dev.azure.com/$organization/$project/_apis/work/teamsettings/iterations?api-version=6.0"

# authentication
$headers = @{
    Authorization = "Basic " + [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(":$($pat)"))
}

# HTTP GET
$response = Invoke-RestMethod -Uri $baseUrl -Method Get -Headers $headers

# list iterations
$response.value | ForEach-Object {
    Write-Output "Iteration Name: $($_.name)"
    Write-Output "Start Date: $($_.attributes.startDate)"
    Write-Output "End Date: $($_.attributes.finishDate)"
    Write-Output "Path: $($_.path)"
    Write-Output "----------------------------------"
}

# data for new iteration
$body = @{
    name = "blabla"
    attributes = @{
        startDate = (Get-Date).AddDays(1).ToString("yyyy-MM-ddTHH:mm:ssZ")
        finishDate = (Get-Date).AddDays(14).ToString("yyyy-MM-ddTHH:mm:ssZ")
    }
} | ConvertTo-Json 

# HTTP POST
function Add-Iteration {
    param (
        [string]$url,
        [hashtable]$headers,
        [string]$body
    )
    try {
        $response = Invoke-RestMethod -Uri $url -Method Post -Headers $headers -Body $body
        Write-Output "Iteration successfully added:"
        Write-Output $response
    }
    catch {
        Write-Output "Error adding iteration:"
        Write-Output $_.Exception.Message
    }
}

# add iteration
Add-Iteration -url $baseUrl -headers $headers -body $iterationData