can javascript function return multiple values?

Here's what I am doing. I have a form that has four date fields. When date1 is entered, I would like to auto-populate date2, date3, and date4, and show them on the form.

date2 = date1 - 12
date3 = date1 - 28
date4 = date1 - 42

I'm very newbie to javascript and know that I can "onblur" a single field, but I doubt I can do all three at one time that way. I'm thinking these calculations need to happen in a function that is called in the onblur=function(). In doing that, how do I retrieve my 3 new values for display in my form?

Thanks for all your help. You all are great and have been very helpful.