powershell script to delete old files and log what gets deleted

gistfile1.txt

$d = "C:\db\backup"
$today = get-date -uformat "%Y_%m_%d"
$log = "C:\db\backup\" + "Purge_" + $today + ".log"
$a = Get-ChildItem $d -recurse
foreach($x in $a)
{
   $y = ((Get-Date) - $x.CreationTime).Days
   if ($y -gt 3 -and $x.PsISContainer -ne $True)
   {
      $deleted = "Deleting - " + $x.fullname + " - Last Write Time - " + $x.LastWriteTime
      add-content $log -value $deleted 
      $x.Delete()
   }
}