JSFiddle - React, Tailwind, and code Playground

HTML

<ol id="output">
</ol>

JavaScript

var obj = {
    SaturdayClose: "21:00",
    SaturdayOpen: "10:00",
    SundayClose: "12:00",
    SundayOpen: "18:00",
    WeekdayClose: "21:00",
    WeekdayOpen: "10:00"
}, prop, $output = $('#output'), time, x, meridiem;

for (prop in obj) {
    if (obj.hasOwnProperty(prop)) {
        x =+obj[prop].substr(0, 2);
        
        if (x > 12) {
            x = x % 12;
            meridiem = "pm";
        } else {
            meridiem = "am";
        }
        
        time = x + ":00" + meridiem;
        
        $output.append("<li>" + prop + " " + time + "</li>");
    }
}