A small jQuery can meet the requirements. i did not fully test it.
<s c r i p t language="Javascript" src="/js/public/jquery-latest.min.js" type="text/javascript"></s c r i p t>
<s c r i p t>
var $jQ = jQuery.noConflict();
var d = new Date();
var month = d.getMonth()+1;
var day = d.getDate();
var output = d.getFullYear() + '/' +
(month<10 ? '0' : '') + month + '/' +
(day<10 ? '0' : '') + day;
document.getElementById(“Field_Name”).setAttribute("value", output);
</s c r i p t>
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