Uses information from NZ Government to identify if a date is a New Zealand public holiday.

Get-Holiday.ps1

<#
.Synopsis
    Uses information from NZ Government to identify if a date is a New Zealand public holiday.
.DESCRIPTION
    This script pulls the lastest iCal from employment.govt.nz to confirm if a date is a public holiday.
    If a public holiday is found, it's name is returned.

    There is an assumption that the holidays supplied are single day events.
.PARAMETER Date
    The date to be checked.

    Default: The current date
.PARAMETER Region
    If supplied, only the local regional holiday will be considered.

    Valid values: 
.EXAMPLE
    ./Get-Holiday.ps1 
.EXAMPLE
    ./Get-Holiday.ps1 -Date "12/25/2018"
.EXAMPLE
    ./Get-Holiday.ps1 -Date "01/21/2019" -Region Wellington
.NOTES
  Version:        1.2
  Author:         Cameron McConnochie
  Creation Date:  5 Feb 2019
  Purpose/Change: Improved the ics file parsing
  
  Version:        1.1
  Author:         Cameron McConnochie
  Creation Date:  4 Feb 2019
  Purpose/Change: Added Region selection to exclude other regions

  Version:        1.0
  Author:         Cameron McConnochie
  Creation Date:  4 Feb 2019
  Purpose/Change: Initial script development
#>

[CmdletBinding()]
Param(    
    [Parameter(Mandatory=$False)]
    [DateTime]$Date = (Get-Date),

    [Parameter(Mandatory=$False)]
    [ValidateSet("Chatham Islands","Westland","Canterbury","Marlborough","Hawke's Bay","Canterbury (South)","Southland","Otago","Taranaki","Nelson","Auckland","Wellington")]
    [String]$Region
)

#Initalise Variable
$HolidayName = $null

#Grab iCal file
$Content = Invoke-WebRequest "http://apps.employment.govt.nz/ical/public-holidays-all.ics"

#Error Checking
if(-not ($Content.Content.Substring(0,100) -like "BEGIN:VCALENDAR*")){
    throw "Error recieving iCal from employment.govt.nz"
}

#Split the iCal content into individual events
$Events = $Content.Content -split 'BEGIN:VEVENT'

#Process each event
ForEach ($Event in $Events) {
    #Check if the "DTSTART" matches the date we're checking
    If(($Event -split '\r?\n') -contains "DTSTART;VALUE=DATE:$(Get-Date -Date $Date -UFormat '%Y%m%d')") { 
        #Update the HolidayName variable with the "SUMMARY" if the dates match
        $HolidayName = ((($Event -split '\r?\n') | Select-String -Pattern "SUMMARY") -split ':')[1]
    } 
}

#If nothing found on that date, return null
If(-not $HolidayName){
    return $null
}

If ($Region -and $HolidayName -like "*Anniversary*"){ 
    #If a region is supplied, and the Holiday found is a regional anniversary, only return the correct region
    If ($HolidayName -like "*$($Region)*"){
        return $HolidayName
    } else {
        return $null
    }
} else {
    #No Region supplied or the holiday found is not a regional anniversary, return the holday name
    return $HolidayName
}