We will be in Rome 5 nights (July 18-22) then heading on the train to Cinque Terre on July 23. Our original plan was to leave Rome in the morning of the 23rd and arrive in CT about 1:00pm, spend the rest of that day in CT, spend the night and then have another full day 24th in CT. However, would it be better for us to leave Rome the evening of the 22nd, so we would have two full days in CT?

Five nights in Rome means probably 4 1/2 days. For me this is too less, I would not take one more day from Rome to add to CT.
Of course, it depends of your interests.

Well if we left the evening of the 22nd, we would just be taking a few (sightseeing) hours off of Rome. I guess my real question is 1 1/2 days enough time for CT or do we need 2 full days?

Hi, ronnieh -

It is possible to walk the trails between all 5 villages of the Cinque Terre in one day, assuming you are fit and the weather cooperates.

Hope that helps!

I just don't think it's worth going for 1 1/2 days.

We did 1 1/2 days when we were there and thought that was enough time. We arrived at around noon and found a room in Vernazza. After lunch we trained to Riomaggiore and hiked to Corniglia, stopping to explore Manarola along the way. We decided to skip the hike to Vernazza and instead rode the train back. The trails between Monterosso - Vernazza and Vernazza - Corniglia are the most demanding.

We spend the evening dining in Vernazza and exploring the town. The next day we hiked Vernazza to Monterosso and spend a good portion of the day relaxing on the beach there.

Of course you could spend more time there, but we felt it was a nice break from our vacation. We spent a day previously in Florence and returned to Florence for 2 more days after the CT.

Some folks will find 1.5 days in 5 Lands about 1 day too much - others will find one week too little.

If not hiking the towns are tiny and in high season very mobbed.