For a good portion of its history the bitcoin network has seen continuous increases in difficulty, which warps the average block time to be below 10 minutes until the next difficulty adjustment. If the reverse were true the block time would be longer in kind.
This latency serves to protect nodes against isolation attacks where you could otherwise ...
I'm not the author, but found this code:
Top 10 longest (using timestamp in block header, which can vary up to 2 hours from actual time)
Block 1: 2009-01-03 463160 seconds (5 days, ~8 hours)
Block 15324: 2009-05-22 90532 seconds (~25 hours)
Block 16564: 2009-06-05 90390 seconds (~25 hours)
Block 15: 2009-01-09 87157 seconds (...