Can LastAccessTime be set to an old timestamp using PowerShell?

Question

I am using PowerShell to create test files for testing the output of Robocopy logs. To get different combinations of newer and older files, I am setting the file timestamps in the source and destination. However, I am unable to control the LastAccessTime attribute, which is preventing me from creating a file that Robocopy sees as completely identical ("same").

I can set CreationTime and LastWriteTime to any timestamp. But setting the LastAccessTime only refreshes the LastAccessTime to the current date and time.

$Item = New-Item "test.txt" -Force -Value "test"
$Item.CreationTime = "2000-01-01"
$Item.LastWriteTime = "2000-01-01"
$Item.LastAccessTime= "2000-01-01"  # doesn't work
Set-ItemProperty -Path "test.txt" -Name LastAccessTime -Value "2000-01-01"  # also doesn't work
$Item = $(Get-Item -Path "test.txt")  # refresh the $Item otherwise we see a phantom update of LastAccessTime
Write-Host "$($Item.CreationTime)  $($Item.LastWriteTime)  $($Item.LastAccessTime))"

I expected the output to be:

01/01/2000 00:00:00 01/01/2000 00:00:00 01/01/2000 00:00:00

But the actual output was:

01/01/2000 00:00:00 01/01/2000 00:00:00 06/11/2022 17:29:35

If I wait a few seconds and then re-run the last three lines, the LastAccessTime will be changed to the current date and time again.

Is there a way to set the LastAccessTime with PowerShell?

Answer 1

All 3 file timestamps (CreationTime, LastWriteTime, LastAccessTime) can be set with PowerShell.

The timestamps can either be set via the property, or by using the Set-ItemProperty cmdlet. Examples of valid ways to set any of the 3 timestamps:

$Item = New-Item "test.txt" -Force -Value "test"
# all equally valid ways to set timestamp:
$Item.CreationTime = "2000-01-01"
$(Get-Item "test.txt").LastWriteTime = "2000-01-01"
Set-ItemProperty -Path "test.txt" -Name LastAccessTime -Value "2000-01-01"
# see the result
Get-Item "test.txt" | Select CreationTime, LastWriteTime, LastAccessTime | Format-List

Note that setting the LastAccessTime can be unstable because other processes may read files when their timestamps are updated, and thus trigger the LastAccessTime to be updated. Possible culprits that update LastAccessTime include SearchProtocolHost.exe or anti-virus software.