The WM/EncodingTime attribute contains a time stamp of the time at which the content was encoded.
This attribute uses a FILETIME value, which is a 64-bit value representing the number of 100-nanosecond time units elapsed since January 1, 1601. For more information about the FILETIME, see the Windows System Information section of the Platform SDK.
This is not a coded attribute. You must set it manually if you want to include it in your files.