MIT licence copyright notice for derived works

Question

We're thinking of using some open-source MIT-licensed software in one of our web projects (a jQuery datetime plugin).

The first line of the MIT licence is:

Copyright (c) [year] [copyright holders]

If we include the plugin as-is (without making any changes), I understand we need to include the licence with only the original author (though the actual copyright notice at the top of the js file doesn't specify a year):

Copyright (c) 2013 Keith Wood

If we make changes to the plugin, what does the copyright notice become?

Copyright (c) 2013 Keith Wood, 2013 [My name/Company name]

Do you need to include all previous authors or is there another way of handling such a notice?