How can I get the average lastwritetime from multiple files? - powershell

Question

I have a PowerShell script that is modifying multiple files. I would like to verify that they were modified by checking the last write time property and comparing it to the current time minus 30 minutes.
Is there anyway to get the average time from multiple different files?
For example:
$Var = Get-Childitem -path "C:\users\User\Documents\*.txt"
$lastwt = $var.Lastwritetime
If($lastwt -ge (Get-Date).addminutes(-30)){
Do stuff
}
The above won't work because multiple dates are returned all around the same time give or take a few milliseconds.
I want to just get the average of all the times and use that as time comparison instead. Any way to do this?

Answer 1

About
So you should probably use New-Timespan to do time comparisons. So your update code:
Code
$Files = Get-Childitem -path "C:\users\User\Documents*.txt"
$Files | ? {
# Filter by a timespan criteria (last write on this file is greater than 30 minutes before now)
$Mins = New-Timespan $_.LastWriteTime (Get-Date) | % TotalMinutes
return $Mins -ge 30
} | % {
# Work only on files that matched the top criteria
}
Does that help? If you still want the averaging solution, lmk, I'll add it in :)

Answer 2

To get an average (median) LastWriteTime [DateTime] object of a series of files, this may be what you want:
$files = Get-Childitem -Path 'C:\users\User\Documents' -Filter '*txt' -File
# get an array of the LastWriteTime properties and sort that
$dates = $files | Select-Object -ExpandProperty LastWriteTime | Sort-Object
$oldest = $dates[0]
$newest = $dates[-1]
# create a new DateTime object that holds the middle of the oldest and newest file time
$average = [datetime]::new((($oldest.Ticks + $newest.Ticks) / 2), 'Local')
# show what you've got:
Write-Host "Oldest LastWriteTime: $oldest"
Write-Host "Average LastWriteTime: $average" -ForegroundColor Green
Write-Host "Newest LastWriteTime: $newest"