sort by archives in dropdown menu

this code creates a drop down menu with all Categories. i would like to learn how to modify it so it shows Archives instead of categories. i.e. sort posts by months. how should this be done?

thanks

<?php wp_dropdown_categories('show_option_none=Sort by Category'); ?>

	<script type="text/javascript">
    var dropdown = document.getElementById("cat");
    function onCatChange() {
		if ( dropdown.options[dropdown.selectedIndex].value > 0 ) {
			location.href = "<?php echo get_option('home');
?>/?cat="+dropdown.options[dropdown.selectedIndex].value;
		}
    }
    dropdown.onchange = onCatChange;
</script>