Manipulating the date and time environment variables is dependent on your Windows regional settings ... but for the U.S. English default settings for Windows XP, you can use:
md "%date:~-4%-%date:~-10,2%-%date:~-7,2%-%time:~0,2%"
And I guess you would want to substitute the space with a 0 (when the hour is less than 10) like:
set DateHr=%date:~-4%-%date:~-10,2%-%date:~-7,2%-%time:~0,2%
md "%DateHr: =0%"