Increase number each day - powershell

Question

I need to create a variable in PowerShell that increases with one each day. I'm going to use this variable in an email subject to define the Day Number as part of a test schedule. e.g. "Test - Day 38", when the script runs the next day it must ready "Test - Day 39".
I obviously can't use the date and AddDays, because the count is not limited to the number of days in the month.

Answer 1

Here is the code, $days is the result
# when counting starts, the first day
$startDate = [datetime]'2014-01-12'
# elapsed days (+ 1 in order to start with "day 1")
$days = [int]((Get-Date) - $startDate).TotalDays + 1
# result string
"Test - Day $days"
This code outputs (today)
Test - Day 38

Answer 2

Here's what I propose (it does involve using the date cmdlets):
When the test first runs, store the runtime in a file.
For example:
if (!(Test-Path startTime.txt)) {
get-date | out-file startTime.txt
}
Each time the test runs subsequently, read in the first_runtime from the file.
Subtract the current date (using get-date) from first_runtime.
This will have a .Days member you can extract to retrieve the number of Days elapsed.
Days : 2
Hours : 0
...