# put is app_root/public/javascript/application.js

function set_today(model, atrib)
{
    t3 = document.getElementById(model + '_' + atrib + '_3i');
    var dt = new Date();
    t3.selectedIndex = dt.getDate();
       
    t2 = document.getElementById(model + '_' + atrib + '_2i')
    t2.selectedIndex = dt.getMonth() + 1;
   
    t1 = document.getElementById(model + '_' + atrib + '_1i')

    for (i = 0; i < t1.length; i++)
               {
                   if (t1.options[i].text == dt.getFullYear())
                   {
                       t1.selectedIndex = i;
                  }
    }
}

<a href="javascript: set_today('model_name', 'column_name');">today?</a>