In Unix you have the touch command which you can use to update a files timestamp. No such thing in Windows. But instead, apparently, one can do this:
REM Updates the timestamp of the file
copy /b filename.ext +,,
REM Creates a new empty file
echo $null >> filename.ext
copy /b filename.ext +,,
REM Creates a new empty file
echo $null >> filename.ext
If you need it more than seldom there are also some more tricks in the StackOverflow sources below.
Sources:
Windows equivalent of the Linux command ‘touch’?
Equivalent of Linux `touch` to create an empty file with PowerShell?