function valueToTimeStr(value){
    var second = value*24*60*60;
    var h = Math.floor(value*24) ;
    var m  = (value*24 - h)*60;
    var s = second - h*60*60 - m*60;
    return h+":"+m+":"+s;
}
console.log(valueToTimeStr(0.343750));//8:15:0
console.log(valueToTimeStr(0));//0:0:0
console.log(valueToTimeStr(1));//24:0:0

http://blog.stevenlevithan.com/archives/date-time-format