Italian passport with 3 months validity, 24h in Shangai

I'm traveling from London to Osaka via Shanghai. I have a 15h wait between the flights and I would like to exit the airport to visit the city a bit. The problem is my passport has less than 6 months validity? Can i leave the airport even if for normal China visas you need 6 months validity? Do I need the 72h or the 24h?