Vista - Comparing dates with If

I'm trying to find directories more than 90 days old, but it looks like the
If comparison isn't working correctly. In this script the result should be
'True' but comes out 'False'. Suggestions?
# IfTest.ps1
# Test If on date comparison

# Get today's date and calculate the date 90 days ago
$Today = ( get-date ).ToString('MMddyyyy')
$90daysago = ( get-date ).AddDays(-90).ToString('MMddyyyy')

Write-Output $Today
Write-Output $90daysago

# Test difference in dates
If($90daysago -lt $Today)
{$Test = 'True'}
Else
{$Test = 'False'}

Write-Output "Today is later than 90 days ago: " $Test
--
Terry Edwards

The problem is that you're comparing strings, not dates

If you write

$Today = get-date
$90daysago = (get-date).AddDays(-90)

$Today -gt $90daysago

it returns correctly true but if you compare

01072009 with 10092008, the second string is greater than the first one.

In microsoft.public.windows.powershell message <u4nxt6NcJHA.1268@xxxxxx
NGP04.phx.gbl>, Wed, 7 Jan 2009 11:41:10, "Marco Shaw [MVP]" <marco.shaw
@_NO_SPAM_gmail.com> posted:

There is nothing intrinsically wrong with doing that, given that the
year can be assumed to be four-digit. But in this case, the designated
string format is FFF.

Use an ISO 8601 format, and the string comparison will work as desired.

It is foolish to use MMddyyyy within data processing, although
MM/DD/YYYY may be wanted to provide a human interface in a few
countries.

There should, however, be no need to do the expensive conversion to
string; conversion of the representation of true (non-string) numbers
would be much better.

--
(c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05.
Web <URL:http://www.merlyn.demon.co.uk/> - w. FAQish topics, links, acronyms
PAS EXE etc : <URL:http://www.merlyn.demon.co.uk/programs/> - see 00index.htm
Dates - miscdate.htm moredate.htm js-dates.htm pas-time.htm critdate.htm etc.