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FolderDate
Recursively sets each folder's date to the date of the newest file in that folder.
Written in C++ using plain WinAPI, resulting in small executable (only 12 KiB) and no need for any extra dll-files or framework runtimes.

Supports commandline arguments:
folderdate.exe [switches] [folders]
Switches:
/a automatically starts scanning
/s silent, no messagebox popups when finished
You can also use them togheter and process more than one folder at the same time:
folderdate.exe /a /s "C:\Path 1" "D:\More\Path 2" "C:\Even\More\Path 3"