Robocopy , or "Robust File Copy", is a command-line directory replication command. It has been available as part of the Windows Resource Kit starting with Windows NT 4.0, and was introduced as a standard feature of Windows Vista, Windows 7 and Windows Server 2008.
robocopy c:\Sourcepath c:\Destpath /E /XC /XN /XO
To elaborate (using Hydrargyrum, HailGallaxar and Andy Schmidt answers):
/Emakes Robocopy recursively copy subdirectories, including empty ones.
/XCexcludes existing files with the same timestamp, but different file sizes. Robocopy normally overwrites those.
/XNexcludes existing files newer than the copy in the destination directory. Robocopy normally overwrites those.
/XOexcludes existing files older than the copy in the destination directory. Robocopy normally overwrites those.
With the Changed, Older, and Newer classes excluded, Robocopy does exactly what the original poster wants - without needing to load a scripting environment.