This BIOS release was built at 23:02 (11:02 PM) on July 17th 2012. It's actual release date would have been some number of days/weeks after that, depending upon how long it took to clear evaluation and validation processes.
BTW, the build date and time is included within the version string for the BIOS. In this particular case, the version string was BGP6710J.86A.2209.2012.0717.2302,
- The "BGP6710.86A" is the Standard BIOS Identifier for the Burrage (DP67BG) board.
- The "2209" is the BIOS version.
- The "2012.0717.2302" is the build date and time. It is in form "YYYY.MMDD.HHMM".