Let's get a date object containing today's noon:
let now = new Date();
let date = new Date(now.getFullYear(), now.getMonth(), now.getDate(), 12);
And now it's noon tomorrow:
let now = new Date();
let date = new Date(now.getFullYear(), now.getMonth(), now.getDate() + 1, 12);
Determine how many hours have passed between yesterday afternoon and the current point in time.