Update: Now that it\'s 2016 I\'d use PowerShell for this unless there\'s a really compelling backwards-compatible reason for it, particularly because of the regional setting
http://sourceforge.net/projects/unxutils/files/
Look inside the ZIP file for something called "Date.exe" and rename it "DateFormat.exe" (to avoid conflicts).
Put it in your Windows system32 folder.
It has a lot of "date output" options.
For help, use DateFormat.exe --h
I'm not sure how you would put its output into an environment variable... using SET.