JSFiddle - React, Tailwind, and code Playground

HTML

<body ng-app="app">
    <label for="start">From:</label>
    <input type="date" ng-model="startDate" string-to-timestamp />
    
    <div>Timestamp: {{startDate}}</div>
</body>

JavaScript

angular.module('app', [])
    .directive('stringToTimestamp', function() {
        return {
            require: 'ngModel',
            link: function(scope, ele, attr, ngModel) {
                // view to model
                ngModel.$parsers.push(function(value) {
                    return Date.parse(value);
                    //return new Date(value).getTime();
                });
            }
        }
    });