Uncaught TypeError: .indexOf is not a function

I am new to JavaScript and I’m getting an error as below.

Uncaught TypeError: time.indexOf is not a function

Gee, I really thought indexOf() really was a function. Here is a snippet of my code:

    var timeofday = new Date().getHours() + (new Date().getMinutes()) / 60;
    document.getElementById("oset").innerHTML = timeD2C(timeofday);
</script>


<script>
 function timeD2C(time) { // Converts 11.5 (decimal) to 11:30 (colon)
    var pos = time.indexOf('.');
    var hrs = time.substr(1, pos - 1);
    var min = (time.substr(pos, 2)) * 60;

    if (hrs > 11) {
        hrs = (hrs - 12) + ":" + min + " PM";
    } else {
        hrs += ":" + min + " AM";
    }
    return hrs;
}
</script>