Since the genesis block is hardcoded in the software, what likely happened is Satoshi generated it in advance, added it to the code, and then did a few more days of final testing prior to release. Block #1 on the other hand was mined after the initial announcement on the cryptography mailing list: http://www.metzdowd.com/pipermail/cryptography/2009-January/... (about seven or eight hours after if I got my timezone conversions correct)
Since the genesis block is hardcoded in the software, what likely happened is Satoshi generated it in advance, added it to the code, and then did a few more days of final testing prior to release. Block #1 on the other hand was mined after the initial announcement on the cryptography mailing list: http://www.metzdowd.com/pipermail/cryptography/2009-January/... (about seven or eight hours after if I got my timezone conversions correct)