How to assign an expiry date based on the earliest date of the three date fields

Use this as custom calculation script of "ProductExpiry" field:

var d1 = this.getField("GelExpDate_af_date").valueAsString;
var d2 = this.getField("WFIExpDate_af_date").valueAsString;
var d3 = this.getField("N2ExpDate_af_date").valueAsString;

if(d1 == "" || d2 == "" || d3 == "")
 event.value = "";
else{
 d1 = util.scand("dd/mm/yyyy", d1);
 d2 = util.scand("dd/mm/yyyy", d2);
 d3 = util.scand("dd/mm/yyyy", d3);

var earliestDate = new Date(Math.min(d1, d2, d3));

event.value = util.printd("dd/mm/yyyy", earliestDate);}