How would I simplify a JSON object containing “working hours”?

I’ve got a JSON object with the office hours / working hours specified for each day of the week.
My objective is to be able to simplify the textual output of the object without the need for repeating unnecessary days’ working hours that are the same as the previous day’s working hours.

The current output is as followed:

Monday: 08:00 AM - 21:00 PM
Tuesday: 08:00 AM - 21:00 PM
Wednesday: 08:00 AM - 21:00 PM
Thursday: 08:00 AM - 21:00 PM
Friday: 08:00 AM - 21:00 PM
Saturday: 08:00 AM - 18:00 PM

I’m doing the following to display the textual output of the working hours for each day (it should skip any days with the start and end time set to 00:00 AM - such as Sunday):

// Office hours object
const json_office_hours = '{"Monday":{"start":"08:00 AM","end":"21:00 PM"},"Tuesday":{"start":"08:00 AM","end":"21:00 PM"},"Wednesday":{"start":"08:00 AM","end":"21:00 PM"},"Thursday":{"start":"08:00 AM","end":"21:00 PM"},"Friday":{"start":"08:00 AM","end":"21:00 PM"},"Saturday":{"start":"08:00 AM","end":"18:00 PM"},"Sunday":{"start":"00:00 AM","end":"00:00 AM"}}';
const office_hours = JSON.parse(json_office_hours);


// Iteration
let office_hours_text = "";
let oh_prev_day = "Monday";
for(let day in office_hours) {
    if(office_hours.hasOwnProperty(day)) {
        let oh_start = office_hours[day].start;
        let oh_end = office_hours[day].end;

        if(oh_start !== '00:00 AM' && oh_end !== '00:00 AM') {
            office_hours_text += day + ": " + oh_start + " - " + oh_end + 'n';
        }
        oh_prev_day = day;
    }
}

console.log(office_hours_text);

The simplified output I’m trying to achieve, is the following:

Monday - Friday: 08:00 AM - 21:00 PM
Saturday: 08:00 AM - 18:00 PM

For some reason, I cannot wrap my head around simplifying the output.

Your assistance would be greatly appreciate – and thank you.