Get date for last <day of week>

Get-LastDOW.ps1

function Get-LastDOW {
  <#
    .SYNOPSIS
    Returns the date of the last day of week you select.

    .DESCRIPTION
    Get-LastDOW will return the date of the last day of the week you select,
    up to one week in the past (between one week ago and yesterday). Useful,
    as an example, to search in logs for events only happening once a week.

    .PARAMETER DayOfWeek
    The day of the week you're searching the date for. Either the full name
    of the day or its index in the week.

    .EXAMPLE
    Get-LastDOW -DayOfWeek Sunday
    Gives the date of the last Sunday.

    .INPUTS
    [DayOfWeek] Enumeration.

    .OUTPUTS
    [DateTime]
  #>


  param
  (
    [DayOfWeek]
    [Parameter(Mandatory=$true,HelpMessage='Please provide the day of week')]
    $DayOfWeek
  )
  if ( [int]$DayOfWeek -ge [int]((Get-Date).DayOfWeek) ) { $adjust = 7 } else { $adjust = 0 }
  return (Get-Date).AddDays( ( [int]$DayOfWeek ) - ( [int]((Get-Date).DayOfWeek) ) - $adjust )
}

Get-LastDOW -DayOfWeek Monday
Get-LastDOW -DayOfWeek Tuesday
Get-LastDOW -DayOfWeek Wednesday
Get-LastDOW -DayOfWeek Thursday
Get-LastDOW -DayOfWeek Friday
Get-LastDOW -DayOfWeek Saturday
Get-LastDOW -DayOfWeek Sunday