calculate min variable using Knockout

demo.js

this.min = ko.computed(function () {
        let toDateObj = new Date(this.to_date());
        toDateObj.setFullYear(toDateObj.getFullYear() - 1);
        return ko.observable(ojconverterutils_i18n_1.IntlConverterUtils.dateToLocalIso(toDateObj));
 }, this);