JSFiddle - React, Tailwind, and code Playground

JavaScript

console.log(dateToEpoch(new Date()));
console.log(dateToEpoch(new Date(1408704590485)));

console.log(dateToEpoch(new Date()));
console.log(dateToEpoch(new Date(1408704590485)));


function dateToEpoch(thedate) {
    var time = thedate.getTime();
    return time - (time % 86400000);
}

function dateToEpoch2(thedate) {
    return thedate.setHours(0,0,0,0).getTime();
}