We recently had a discussion with a client about estimation. From the developer point of view it's hard to predict the date because of many things which might happen during development and we are not aware yet about them at the moment when we need to declare the date.

Now we are using historical data to predict how many calendar days the features scope may take with a specific confidence level.

From the client perspective dates are important because they need to coordinate release of multiple projects and dates help them release right stuff, in right order, in right moment on production.

Here is article about our approach http://blog.lunarlogic.io/2015/project-management-estimation...