JSFiddle - React, Tailwind, and code Playground

HTML

<input data-bind="value : rawDate" type="date">
<hr>   
<span data-bind="html: log" />

JavaScript

var currentDate = (new Date()).toISOString().split('T')[0];

var viewModel = {    
    rawDate : ko.observable(currentDate),
    log : ko.observable(""),
    logDate : function () { 
            this.log(this.log() + this.MyDate() + " : " +
                     typeof(this.MyDate()) + "<br>");
                     }
};

viewModel.MyDate = ko.computed(function () {
    var val = this.rawDate();
    if (typeof val === 'string') val = new Date(val);
    
    return val;
}, viewModel)

viewModel.MyDate.subscribe(function (date) {    
    viewModel.logDate();    
});

ko.applyBindings(viewModel);

viewModel.logDate()