The NBBO prices used in OneChronos auctions are the SIP derived prices most recent to but not after the Auction Initialization Time. As an illustrative example of this procedure: 1. Auction Initialization results in an auction cutoff time; 2. Auction Network Buffering allows data to propagate from exchanges, to the SIP, and ultimately to the OneChronos ATS; 3. After buffering the ATS computes NBBO for each tradable symbol by processing all messages from the SIP with Exchange Timestamps less than or equal to the cutoff time for the auction.