Powershell script to change account expiration

Hello,

I'm very new at scripting but I have the following script

Import-Module ActiveDirectory

import-csv C:\Users\jpratt\Desktop\book1.csv |
ForEach{
#set expiration date

$expire = read-host -prompt "Should this account expire y/n"
if ($expire -eq "y") {
$expirationdate = read-host -prompt "enter expiration date mm/dd/yy"
$time = [datetime]"$expirationdate" - (Get-Date)
$days = $time.days
Write-Host $days
dsmod user "$userDN" -acctexpires $days
 }
 }

I am getting a DSMOD error so Im thinking it is something simple im overlooking.  I do get the popup asking me to input the date I want it to expire.

Thanks for any help,