in google-cloud-server/src/main/resources/buildServerResources/knockout.validation-2.0.3.js [924:927]
validator: function (value, validate) {
if (!validate) { return true; }
return kv.utils.isEmptyVal(value) || (validate && /^\d{4}[-/](?:0?[1-9]|1[012])[-/](?:0?[1-9]|[12][0-9]|3[01])$/.test(value));
},