Also note that it's his 67th birthday. Since the party was held in December 1958, that'd give him a birth year of 1891.

What's interesting to me is that, in a deleted scene after Sr. Roberto leaves young Vito's office shaking like a leaf, young Clemenza introduces him to young Roth. Vito looks to be about 30 in that scene; Roth looks to be 17 or 18. But, the birthday cake in Havana would make Vito and Roth about ths same age.