Powershell scripts to export calendar events from outlook to ics

export.ps1

. ".\Get-OutlookCalendar.ps1"
. ".\Format-String-Ics.ps1"
. ".\New-IcsEvent.ps1"

$ErrorActionPreference = "Stop"

Get-OutlookCalendar | New-IcsEvent -CalendarName "your email" -CalendarTimezone "Europe/Stockholm" -CalendarDescription "Your Calendar Name" -OutputPath .\export.ics -CalendarDomain "example.com"
Invoke-WebRequest -Method PUT -Infile .\export.ics -Uri https://your-ics-server.here

Format-String-Ics.ps1

function Format-String-Ics([string] $Body) {
  $Str = $Body.Replace("`n", "\n").Replace("`r", "")
  $Result = ""
  [Int]$i = 0
  while (($Str.Length - $i) -gt 60) {
    $next = [math]::Min($i + 60, $Str.Length - 1)
    $Result = "$Result$($Str.Substring($i, $next - $i))`r`n "
    $i = $next
  }
  if ($i -eq 0) {
    return $Str
  }
  else {
    return "$Result$($Str.Substring($i, $Str.Length - $i))"
  }
}

Get-OutlookCalendar.ps1

function Get-OutlookCalendar {
  <#
   .Synopsis
    This function returns appointment items from default Outlook profile
   .Description
    This function returns appointment items from default Outlook profile. It
    uses the Outlook interop assembly to use the olFolderCalendar enumeration.
    It creates a custom object consisting of Subject, Start, Duration, Location
    for each appointment item.
   .Example
    Get-OutlookCalendar |
    where-object { $_.start -gt [datetime]”5/10/2011″ -AND $_.start -lt `
    [datetime]”5/17/2011″ } | sort-object Duration
    Displays subject, start, duration and location for all appointments that
    occur between 5/10/11 and 5/17/11 and sorts by duration of the appointment.
    The sort is shortest appointment on top.
   .Notes
    NAME:  Get-OutlookCalendar
    AUTHOR: ed wilson, msft
    LASTEDIT: 05/10/2011 08:36:42
    KEYWORDS: Microsoft Outlook, Office
    HSG: HSG-05-24-2011
   .Link
     Http://www.ScriptingGuys.com/blog
 #Requires -Version 2.0
 #>
  #Add-Type -Path $env:WINDIR\assembly\GAC_MSIL\office\15.0.0.0__71e9bce111e9429c\office.dll
  Add-Type -Path $env:WINDIR\assembly\GAC_MSIL\Microsoft.Office.Interop.Outlook\15.0.0.0__71e9bce111e9429c\Microsoft.Office.Interop.Outlook.dll

  #Add-type -assembly "Microsoft.Office.Interop.Outlook" | out-null
  $olFolders = "Microsoft.Office.Interop.Outlook.OlDefaultFolders" -as [type]
  $outlook = new-object -comobject outlook.application
  $namespace = $outlook.GetNameSpace("MAPI")
  $folder = $namespace.getDefaultFolder($olFolders::olFolderCalendar)
  $folder.items
} #end function Get-OutlookCalendar

New-IcsEvent.ps1

function Get-Byday {
  [CmdletBinding()]
  param (
    [Parameter(Mandatory)]
    [int]
    $BitMask
  )

  $MaskTable = @{
    1  = "SU"
    2  = "MO"
    4  = "TU"
    8  = "WE"
    16 = "TH"
    32 = "FR"
    64 = "SA"
  }


  $arr = $()
  foreach ($WeekDay in $MaskTable.Keys | Sort-Object) {
    if ($BitMask -band $WeekDay) {
      $arr += , $MaskTable[$WeekDay]
    }
  }

  $arr -join ','

}
function Format-Date {
  [CmdletBinding()]
  param (
    [Parameter(Mandatory)]
    [datetime]
    $Date
  )
  # Custom date formats that we want to use
  $icsDateFormat = "yyyyMMddTHHmmssZ"

  $Date.ToUniversalTime().ToString($icsDateFormat)
}
function Get-Email {
  [CmdletBinding()]
  param (
    [Parameter(Mandatory)]
    [string]
    $String,
    [Parameter(Mandatory)]
    [string]
    $CalendarDomain
  )

  # TODO: make something better than this
  "$($String.ToLower().Replace(" ", ".").Replace("@", ''))@$CalendarDomain"
}
function Get-Recur {
  [CmdletBinding()]
  param (
    [Parameter(Mandatory)]
    $FullEvent
  )

  $Pattern = $FullEvent.GetRecurrencePattern()
  [datetime]$PatternEndDate = $Pattern.PatternEndDate
  #[datetime]$PatternStartDate = $Pattern.PatternStartDate
  #[int]$DayOfMonth = $Pattern.DayOfMonth
  [int]$DayOfWeekMask = $Pattern.DayOfWeekmask
  [int]$Interval = $Pattern.Interval
  [int]$RecurrenceType = $Pattern.RecurrenceType

  if ($RecurrenceType = 1) {
    # Weekly
    return Format-String-Ics "RRULE:FREQ=WEEKLY;INTERVAL=$Interval;UNTIL=$(Format-Date $PatternEndDate);BYDAY=$(Get-Byday $DayOfWeekMask)"
  }

  # TODO: Support other RecurrenceTypes
  return ""
}

function New-IcsEvent {
  [OutputType([System.IO.FileInfo[]])]
  [CmdletBinding(SupportsShouldProcess, ConfirmImpact = 'Low')]
  param
  (
    [Parameter(Mandatory)]
    [string]
    $OutputPath,
    [Parameter(Mandatory)]
    [string]
    $CalendarName,
    [Parameter(Mandatory)]
    [string]
    $CalendarTimezone,
    [Parameter(Mandatory)]
    [string]
    $CalendarDescription,
    [Parameter(Mandatory)]
    [string]
    $CalendarDomain,

    [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
    [datetime]
    $Start,

    [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
    [datetime]
    $End,

    [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
    [datetime]
    $CreationTime,

    [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
    [datetime]
    $LastModificationTime,


    [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
    [string]
    $Subject,

    [Parameter(ValueFromPipelineByPropertyName)]
    [string]
    $Location,

    [Parameter(ValueFromPipelineByPropertyName)]
    [int]
    $Duration = 60,

    [Parameter(ValueFromPipelineByPropertyName)]
    [string]
    $Body,

    [Parameter(ValueFromPipelineByPropertyName)]
    [bool]
    $IsRecurring,

    [Parameter(ValueFromPipelineByPropertyName)]
    [bool]
    $AllDayEvent,

    [Parameter(ValueFromPipelineByPropertyName)]
    [string]
    $RequiredAttendees,

    [Parameter(ValueFromPipelineByPropertyName)]
    [string]
    $Organizer,

    [Parameter(ValueFromPipelineByPropertyName)]
    [string]
    $OptionalAttendees,

    [Parameter(ValueFromPipeline)]
    $FullEvent,

    [ValidateSet('Free', 'Busy')]
    [string]
    $ShowAs = 'Busy',

    [ValidateSet('Private', 'Public', 'Confidential')]
    [string]
    $Visibility = 'Public'
  )

  begin {
    $calStart = @"
BEGIN:VCALENDAR
PRODID:-//Google Inc//Google Calendar 70.9054JHP//EN
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:$CalendarName
X-WR-TIMEZONE:$CalendarTimezone
X-WR-CALDESC:$CalendarDescription
"@

    $calEnd = @"
END:VCALENDAR
"@

    $fileName = $OutputPath

    $calStart | Out-File -FilePath $fileName -Encoding utf8 -Force
  }

  end {
    $calEnd | Out-File -FilePath $fileName -Encoding utf8 -Force -Append
  }


  # Checkout RFC 5545 for more options
  process {
    $Now = Get-Date

    $dateOnlyFormat = "yyyyMMdd"
    if ($AllDayEvent) {
      $StartString = "DTSTART;VALUE=DATE:$($Start.ToString($dateOnlyFormat))"
      $EndString = "DTEND;VALUE=DATE:$($End.ToString($dateOnlyFormat))"
    }
    else {
      $StartString = "DTSTART:$(Format-Date $Start)"
      $EndString = "DTEND:$(Format-Date $End)"
    }
    $AttendeesArray = @()
    $RequiredArray = $RequiredAttendees.Split(';') 
    $OptionalArray = $OptionalAttendees.Split(';')

    foreach ($a in $RequiredArray) {
      $role = 'REQ-PARTICIPANT'
      $a = $a.Trim()
      if ($a) {
        $s = Format-String-Ics "ATTENDEE;CN=`"$a`";ROLE=$($role):mailto:$(Get-Email $a $CalendarDomain)"
        $AttendeesArray += , $s
      }
    }
    foreach ($a in $OptionalArray) {
      $role = 'OPT-PARTICIPANT'
      $a = $a.Trim()
      if ($a) {
        $s = Format-String-Ics "ATTENDEE;CN=`"$a`";ROLE=$($role):mailto:$(Get-Email $a $CalendarDomain)"
        $AttendeesArray += , $s
      }
    }

    $AttendeesString = $AttendeesArray -join "`r`n"

    $optional = ""
    if ($IsRecurring) {
      $recur = Get-Recur $FullEvent
      if ($recur) {
        $optional += "$recur`r`n"
      }
    }
    if ($AttendeesString) {
      $optional += "$AttendeesString`r`n"
    }


    $eventObj = @"
BEGIN:VEVENT
UID:$([guid]::NewGuid())@$CalendarDomain
CREATED:$(Format-Date $CreationTime)
DTSTAMP:$(Format-Date $Now)
LAST-MODIFIED:$(Format-Date $LastModificationTime)
CLASS:$Visibility
SEQUENCE:0
$StartString
$EndString
DESCRIPTION:$(Format-String-Ics($Body))
SUMMARY:$(Format-String-Ics($Subject))
ORGANIZER;CN=`"$Organizer`":mailto:$(Get-Email $Organizer $CalendarDomain)
LOCATION:$(Format-String-Ics($Location))
TRANSP:$(if($ShowAs -eq 'Free') {'TRANSPARENT'} else {'OPAQUE'})
$($optional)END:VEVENT
"@
    if ($PSCmdlet.ShouldProcess($fileName, 'Write ICS file')) {
      $eventObj | Out-File -FilePath $fileName -Encoding utf8 -Force -Append
    }
  }
}