I'd guess 1965 ish, possibly a bit earlier but I can't say definitively. It was well before my time. Looks like a 151 crank and the derailleur is record not nuovo record, which means the bike dates to 62-66.

If the bike got raced, which is likely, it's easy to imagine that model 61 brakes would have been upgraded with model 68 when they came out.

That's the prettiest Bianchi I've seen in a while. Thanks for posting.