The date of a file can be set or manipulated arbitrarily with PowerShell. In the screenshot you can see a few example values that have been set arbitrarily. The procedure has been tested with Windows PowerShell 5.1.

With Get-Member you can display the time attributes of a file.

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Get-Item example.txt | Get-Member *time*

File date attributes displayed

The interesting attributes are:

  • CreationTime (when the file was created)
  • LastAccessTime (when the file was last accessed)
  • LastWriteTime (when the file was last modified)

As you can see from the {get;set;} at the end, you can not only read these attributes, but also set them.

Examples

In the following examples I show how to change the modification date, the last access time, and the creation timestamp for individual files or all files in a folder.

Notes on the examples

Generate a date

I prefer to generate the date in the following format: 2020-09-13T13:37:37 (see also ISO 8601), or alternatively simplified as 2020-09-13 13:37. This standardized format works independently of OS localization.

Abbreviations and aliases

With gci (abbreviation/alias for Get-ChildItem) we read all items (folders and files) in the current folder. With % (alias for ForEach-Object) we iterate through all items.

Change the creation date

Examples for changing the creation date (“Created”):

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# Set the creation date of all items in the current folder to 1991-11-06 12:03
gci | %{$_.CreationTime=(Get-Date "1991-11-06 12:03")}

# Set the creation date of a specific file to 1991-11-06 12:03
Get-Item "Example.txt" | %{$_.CreationTime=(Get-Date "1991-11-06 12:03")}

Change the modification date

Examples for changing the modification date (“Modified”):

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# Set the modification date of all items in the current folder to 2021-05-01 17:01
gci | %{$_.LastWriteTime=Get-Date "2021-05-01 17:01"}

# Set the modification date of a specific file in the current folder to 2021-05-01 17:01
Get-Item "Example.txt" | %{$_.LastWriteTime=Get-Date "2021-05-01 17:01"}

Change the last access date

Examples for changing the access timestamp (“Last Access”):

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# Set the access date of all items in the current folder to 2019-01-06 08:03
gci | %{$_.LastAccessTime=(Get-Date "2019-01-06 08:03")}

# Set the access date of a specific item in the current folder to 2019-01-06 08:03
Get-Item "Example.txt" | %{$_.LastAccessTime=(Get-Date "2019-01-06 08:03")}

Conclusion

Because the time attributes of files can be manipulated arbitrarily, they should not be trusted. They can at best be used as a clue for an action in a system. But they are definitely not proof.