これを
if (((Get-Date $datrep)-(Get-Date $datchr)).Days -gt 5) { # compare time diff
こういう風に丁寧書きならいけるかもしれません
$aaa=Get-Date $datrep
$bbb=Get-Date $datchr
$ccc=$aaa-$bbb
if ($ccc.Days -gt 5) { # compare time diff

試さなくてもいいですけど