SharePoint Online: Create Date and Time Column in List using PowerShell

• Browse to your SharePoint Online site and then Navigate to the target list in which you want to create date and time column.
• Under the List tab, click on "Create Column" button in the ribbon.
• Provide the Name to your new column, specify the type as "Date and Time" 
• Fill other optional values and Click on "OK" to create date and time column in SharePoint Online list.

#Load SharePoint CSOM Assemblies
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.dll"
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.Runtime.dll"

#Custom function to add column to list
Function Add-DateTimeColumnToList()
{ 
    param
    (
        [Parameter(Mandatory=$true)] [string] $SiteURL,
        [Parameter(Mandatory=$true)] [string] $ListName,
        [Parameter(Mandatory=$true)] [string] $Name,
        [Parameter(Mandatory=$true)] [string] $DisplayName,
        [Parameter(Mandatory=$true)] [string] $Description,
        [Parameter(Mandatory=$true)] [string] $Format,
        [Parameter(Mandatory=$true)] [string] $IsRequired,
        [Parameter(Mandatory=$true)] [string] $FriendlyDisplayFormat,
        [Parameter(Mandatory=$true)] [string] $EnforceUniqueValues
    )

    #Generate new GUID for Field ID
    $FieldID = New-Guid

    Try {
        $Cred= Get-Credential
        $Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.Username, $Cred.Password)

        #Setup the context
        $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
        $Ctx.Credentials = $Credentials

        #Get the List
        $List = $Ctx.Web.Lists.GetByTitle($ListName)
        $Ctx.Load($List)
        $Ctx.ExecuteQuery()

        #Check if the column exists in list already
        $Fields = $List.Fields
        $Ctx.Load($Fields)
        $Ctx.executeQuery()
        $NewField = $Fields | where { ($_.Internalname -eq $Name) -or ($_.Title -eq $DisplayName) }
        if($NewField -ne $NULL)  
        {
            Write-host "Column $Name already exists in the List!" -f Yellow
        }
        else
        {
            #Define XML for Field Schema
            $FieldSchema = "<Field Type='DateTime' ID='{$FieldID}' Name='$Name' StaticName='$Name' DisplayName='$DisplayName' Format='$Format' Required='$IsRequired'  Description='$Description' EnforceUniqueValues='$EnforceUniqueValues' FriendlyDisplayFormat='$FriendlyDisplayFormat' />"
            $NewField = $List.Fields.AddFieldAsXml($FieldSchema,$True,[Microsoft.SharePoint.Client.AddFieldOptions]::AddFieldInternalNameHint)
            $Ctx.ExecuteQuery()    

            Write-host "New Column Added to the List Successfully!" -ForegroundColor Green  
        }
    }
    Catch {
        write-host -f Red "Error Adding Column to List!" $_.Exception.Message
    }
} 

#Set parameter values
$SiteURL="https://crescent.sharepoint.com"
$ListName="Projects"
$Name="ProjectStartDate" #Column Name
$DisplayName="Project Start Date"
$Description="Enter the Project Start Date"
$Format="DateOnly" #DateTime
$IsRequired = "FALSE"
$EnforceUniqueValues="FALSE"
$FriendlyDisplayFormat="Disabled" #Relative

#Call the function to add column to list
Add-DateTimeColumnToList -SiteURL $SiteURL -ListName $ListName -Name $Name -DisplayName $DisplayName -IsRequired $IsRequired -Format $Format -EnforceUniqueValues $EnforceUniqueValues -FriendlyDisplayFormat $FriendlyDisplayFormat -Description $Description