JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.0/knockout-min.js"></script>
<input style="width: 80px" type="time" placeholder="HH:MM" required="" data-bind="value: FirstManifest.Time">

JavaScript

// Here's my data model
var ViewModel = function() {
    this.FirstManifest = ko.observable("/Date(1464748440000)/");

    this.FirstManifest.Time = ko.computed(function() {
        return new Date(parseInt("/Date(1464748440000)/".replace("/Date(", "").replace(")/",""), 10)).toLocaleTimeString();
    }, this);
    
};
 
ko.applyBindings(new ViewModel());