On the 1930 census it should give age at time of marriage. Just take the age at marriage and the age they were in the 1930 census, and that tells you how long they are married for. Take that number and subtract from 1930. That is an approximate marriage year. Try this site for searching for the marriage certificate. http://www.italiangen.org/databaselist.stm
I hope I was able to be of some assistance.