Return the most recent 'Patch Tuesday' date in YYYY-MM-DD format

Get-MostRecentPatchTuesday.ps1

#region --------------------------------------- Get-PatchTuesday
# --- Modified from: https://github.com/tsrob50/Get-PatchTuesday
# --------------------------------------------------------------
Function Get-PatchTuesday {
    [CmdletBinding()]
    Param
    (
        [Parameter(position = 0)]
        [ValidateSet('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday')]
        [String]$weekDay = 'Tuesday',
        [ValidateRange(0, 5)]
        [Parameter(position = 1)]
        [int]$findNthDay = 2
    )

    [datetime]$today = [datetime]::NOW

    function Calculate($date) {
        $dateM = $date.Month.ToString()
        $dateY = $date.Year.ToString()
        [datetime]$strtMonth = $dateM + '/1/' + $dateY
        while ($strtMonth.DayofWeek -ine $weekDay) { $strtMonth = $StrtMonth.AddDays(1) }
        $firstWeekDay = $strtMonth
    
        # -- Identify and calculate the day offset
        if ($findNthDay -eq 1) { $dayOffset = 0 } else { $dayOffset = ($findNthDay - 1) * 7 }
        return $firstWeekDay.AddDays($dayOffset)
    }
    # -- Determine patch tuesday for this current month --------
    [datetime] $patchTuesday = Calculate $today
 
    if ($today -lt $patchTuesday) { 
        return $(Calculate $today.AddMonths(-1)).ToString('yyyy-MM-dd')
    }
    else { return $patchTuesday.ToString('yyyy-MM-dd') }
}
#endregion -----------------------------------------------------

# ------------------------------------------------ Usage Example
# --------------------------------------------------------------
$mostRecentPatchTuesday = Get-PatchTuesday 
Write-Host $mostRecentPatchTuesday # 2021-03-09