Delete events in resource calendars

Recently, as part of a tenant-to-tenant migration, I ran into a problem where a customer had included all of their resource calendars (conference rooms, reservable equipment) in calendar migrations.

Unfortunately, once you’re no longer in the source tenant, you don’t have a way to cancel the meetings.

Until now.

[cmdletbinding()]
param(
[Parameter(Mandatory=$True)][string[]]$UserId,
[Parameter(Mandatory=$True)][string]$ItemsBeforeDate,
[string]$Logfile = (Get-Date -Format yyyy-MM-dd) + "_CalendarEntryProcessing.txt"
)

## Prerequisites
# Graph Calendar module
If (Get-Module -ListAvailable Microsoft.Graph.Calendar) { Import-Module Microsoft.Graph.Calendar }
Else { Throw "Install the Microsoft.Graph.Calendar module before continuing."; Break }

# Graph scopes
[string[]]$CurrentContextScopes = (Get-MgContext).Scopes
[string[]]$RequiredScopes = @('User.Read.All','Calendars.ReadWrite.Shared','Calendars.ReadWrite')
$Intersection =[object[]][Linq.Enumerable]::Intersect($RequiredScopes,$CurrentContextScopes)
If ($Intersection.Count -ne 3) { "Disconnect-MgGraph, then run Connect-MgGraph -Scopes User.Read.All,Calendard.ReadWrite.Shared,Calendars.ReadWrite." }

function Write-Log([string[]]$Message, [string]$LogFile = $Script:LogFile, [switch]$ConsoleOutput, [ValidateSet("SUCCESS", "INFO", "WARN", "ERROR", "MANUAL")][string]$LogLevel)
    {
        $Message = $Message + $Input
        If (!$LogLevel) { $LogLevel = "INFO" }
        switch ($LogLevel)
        {
            SUCCESS { $Color = "Green" }
            INFO { $Color = "White" }
            WARN { $Color = "Yellow" }
            ERROR { $Color = "Red" }
            MANUAL { $Color = "Gray" }
        }
        if ($Message -ne $null -and $Message.Length -gt 0)
        {
            $TimeStamp = [System.DateTime]::Now.ToString("yyyy-MM-dd HH:mm:ss")
            if ($LogFile -ne $null -and $LogFile -ne [System.String]::Empty)
            {
                Out-File -Append -FilePath $LogFile -InputObject "[$TimeStamp] [$LogLevel] $Message"
            }
            if ($ConsoleOutput -eq $true)
            {
                Write-Host "[$TimeStamp] [$LogLevel] :: $Message" -ForegroundColor $Color
            }
        }
    }

$WatershedDate = [DateTime]::Parse($ItemsBeforeDate)
$UserIdTotal = $UserId.Count
$UserIdCounter = 1

Write-Host "Watershed date set to $($WatershedDate)."

Foreach ($User in $UserId)
    {
        Write-Log -LogFile INFO -ConsoleOutput -Message "Processing $($User)"
        # Get events in mailbox
        $UserAlias = $User.Split("@")[0]

        try { $Events = Get-MgUserEvent -UserId $User -All -ErrorAction SilentlyContinue }
        catch { Write-Log -Message "No calendar events found in mailbox $($User)" -LogFile $Logfile -LogLevel INFO }
        $EventTotal = $Events.Count
        $EventCounter = 1
        If ($EventTotal -ge 1)
            {
                Foreach ($Entry in $Events)
                    {
                    Write-Log -ConsoleOutput -LogLevel INFO -Message "Processing calendar entry [$($EventCounter)/$($EventTotal)]"
                    $EntryOrganizer = $Entry.Organizer.Emailaddress.Address.Split("CN=")[2]
                    [datetime]$EntryEndDate = $Entry.End.DateTime

                    If (($Entry.CreatedDateTime -lt $WatershedDate) -and ($EntryEndDate -ge $WatershedDate))
                        {
                         Write-Log -ConsoleOutput -LogLevel INFO -Message "MAILBOX: $($User) || ENTRYENDDATE: $($EntryEndDate)"
                            If (($EntryOrganizer -ne $UserAlias) -or ($IsOrganizer -eq $False))
                            {
                                Write-Log -ConsoleOutput -LogLevel INFO $Logfile -Message "[$($EventCounter)/$($EventTotal)] Calendar Entry SUBJECT: $($Entry.Subject) in MAILBOX $($User) with ID $($Entry.Id) should be deleted because it is older than the watershed date of $($WatershedDate)." 
                                $Remove = Remove-MgUserEvent -UserId $User -EventId $($Entry.Id) -confirm:$false -erroraction SilentlyContinue -PassThru
                                If ($Test = Get-MgUserEvent -UserId $User -EventId $Entry.Id -ErrorAction SilentlyContinue) { Write-Log -ConsoleOutput -LogLevel ERROR -LogFile $Logfile -Message "Calendar Entry SUBJECT: $($Entry.Subject) in MAILBOX $($User) with ID $($Entry.Id) must be deleted manually." }
                            }
                            Else
                            {
                                Write-Log -Logfile $Logfile -LogLevel MANUAL -ConsoleOutput -Message "Calendar Entry SUBJECT: $($Entry.Subject) in MAILBOX $($User) with ID $($Entry.Id) must be deleted manually because $($User) is the ORGANIZER."
                            }
                        }
                    Else
                        {
                            Write-Log -ConsoleOutput -Message "Calendar Entry $($Entry.Subject) with ID $($Entry.Id) in mailbox $($User) was not deleted because it was newer than the watershed date of $($WatershedDate) or was filtered out because its occurrence was older than the watershed date of $($WatershedDate)." -LogLevel INFO -LogFile $Logfile
                        }
                    $EventCounter++
                    }
            }
        $UserIdCounter++
    }

There are a couple of key parameters here:

• UserId parameter is typed as [string[]], so you can provide one or more comma-separated SMTP addresses, an array object, pipe in a CSV, add it to a foreach loop, or however you can get the data in.
• ItemsBeforeDate is the watershed date (in my case, it needed to be the migration cutover date), and it has the following logic:
  • All calendar entries before this date will be ignored
  • Calendar entries created before this date with an instance ending after this date will be deleted
  • If the entry is marked IsOrganizer -eq $True it will be skipped. Entries marked IsOrganizer -eq $True means that the resource mailbox is the organizer, and currently, the Graph cmdlets don’t have an option to suppress sending a cancellation. Due to the way the cmdlet is written, there’s no override or ignore the error, so it’s a terminating failure.  As long as the conference rooms is added as a resource, though, this should be an edge case.

Delete those calendar items with impunity.