Trying to put together a script for automatic timezone updates - powershell

Question

I am working on a powershell script and it isn't reading my "If, elseIf" properly so I know I am doing something wrong. I need some help figuring this out.
I start with pulling the Default Gateway and storing it:
$Gateway = (Get-wmiObject Win32_networkAdapterConfiguration | ?{$_.IPEnabled}).DefaultIPGateway
Next I am trying to get it to sort that so that if it equals one of my designated Default Gateways it will update the timezone.
If ($Gateway = "10.100.4.1")
{
$TZ = "Central Standard Time"
}
ElseIf ($Gateway = "10.101.4.1")
{
$TZ = "Central Standard Time"
}
and I am finishing it up with a
Set-TimeZone $TZ
The purpose is that if I image a system at the home office, and I ship it to "remote location" I can't trust an end user to update their time zone, and I have POS that was poorly written so that it doesn't use UTC/GMT, and can cause issues with the BOH systems et cetera.
I will be placing this in as a startup item to execute whenever the system starts up to ensure that it is always up to date with the TZ.
Changing the Win 10 to use an automatic update for the TZ doesn't work because reasons (read: Networking Team and Security Team are out to get me and in this instance it isn't paranoia).
So, where can I find help to put this all together?
Edit: I had a typo which is why it wasn't working. So... nevermind. For those ofyou interested in the typo, I removed it already. it was in my $Gateway portion, adding a " after {$_.IPEnabled} and before the )

Answer 1

Your "if" statements are using the assignment operator = instead of the equality operator, -eq.
Switch it to If ($Gateway -eq "10.100.4.1") and it should work.
P.S. I missed the typo you mentioned, but the assignment operator is still an issue. When the assignment operator is used in an "if/elsif" statment it will always return $true which would be rather problematic.

Answer 2

I would suggest using a lookup Hashtable for the designated default gateways.
Because you want this to be run as startup script, you also need to create a centralized path where errors can be logged or write errors in the windows eventlog.
Create a Hashtable with your designated gateway IP addresses as key and the timezone ids as value.
Either directly in code:
$timeZones = #{
'10.100.4.1' = 'Central Standard Time'
'10.101.4.1' = 'Central Standard Time'
'10.102.4.1' = 'Eastern Standard Time'
# etc.
}
Or by reading a centralized CSV file with columns 'IPAddress' and 'TimeZone'
$defaultTz = Import-Csv -LiteralPath '\\Server\Share\Folder\Timezones.csv'
$timeZones = #{}
$defaultTz | ForEach-Object {
$timeZones[$_.IPAddress] = $_.TimeZone
}
Next, use these values something like this (demo uses a centralized error log file):
$errorlog = '\\Server\Share\Folder\TimezonesErrors.log'
$now = (Get-Date).ToString() # use default format or specify the date format yourself here
$currentTz = (Get-TimeZone).Id # get the current timezone Id
# get the default gateway IPv4 address for this computer
$gw = #((Get-wmiObject Win32_networkAdapterConfiguration | Where-Object {$_.IPEnabled -and $_.DefaultIPGateway-like '*.*.*.*'}).DefaultIPGateway)[0]
# check if the gateway IP address is present in the lookup Hashtable
if ($timeZones.ContainsKey($gw)) {
$tz = $timeZones[$gw]
# only set the wanted timezone if it differs from the current timezone
if ($tz -ne $currentTz) {
try {
Set-TimeZone -Id $tz -ErrorAction Stop
}
catch {
# add the exception to the error log
$msg = "$now - Error setting the timezone on computer $($env:COMPUTERNAME): $_.Exception.Message"
Add-Content -LiteralPath $errorlog -Value $msg
}
}
}
else {
# make it known that the IP address for this gateway was not found in the Hashtable
$msg = "$now - No timezone found for default gateway $gw on computer $($env:COMPUTERNAME)"
# write error to the central error.log file
Add-Content -LiteralPath $errorlog -Value $msg
}