JSFiddle - React, Tailwind, and code Playground

by Michel Plungjan

HTML

<p id="times">Sun: 18:00a - 12:00p Mon - Sat: 10:00a 21:00p Sat: 12:15p - 00:30a</p>

JavaScript

var re=/(\d{2}:\d{2}[ap])/gi
var times = document.getElementById('times').innerHTML;
var mil = times.match(re);
for (var i=0;i<mil.length;i++) {
    var parts = mil[i].split(":");
    var hours = parseInt(parts[0],10);
    if (hours > 12) parts[0]=hours-=12;
    else if (hours==0) parts[0]=12
    times=times.replace(mil[i],parts.join(":"))
}
alert(times)
document.getElementById('times').innerHTML = times;