Time from planting to harvest in bananas depends on a lot of factors, but probably most important is having (or creating) a tropical climate. In that climate, with plenty of water, light, and nutrients, many varieties will produce ripe fruit in about a year and some in less than a year. The link below is to a document that shows time from planting to harvest for many different varieties grown in the Philippines. It has lots of other interesting information, too.
http://www.musalit.org/pdf/IN090373_en.pdf