date.toLocaleDateString is not a function

Date.parse returns a number. You are looking for new Date. Or, if time already is a Date instance, just use time.toLocaleDateString() (and make sure it really is in every call to the function)!

function formatTime(time, prefix = "") {
    return typeof time == "object" ? prefix + time.toLocaleDateString() : "";
}

You can use

new Date(date).toLocaleDateString();