A couple of simple time related methods in JavaScript

timeFunctions.js

var time = {};

time.parse = function(str){
    // time since start of day. accepts 24 hour time in 23:59 format
    var strSplit = str.split(":");
    
    var hrInt = strSplit[0];
    var minInt = strSplit[1];
    
    var msInt = hrInt * 60 * 60 * 1000 + minInt * 60 * 1000;
    
    return msInt;
};

time.sinceZero = function(){
    // returns number in milliseconds since start of day
    var now = new Date();
    return (
        now.getHours() * 60 * 60 * 1000
        + now.getMinutes() * 60 * 1000
        + now.getSeconds() * 1000
        + now.getMilliseconds()
    );
};

time.stringify = function(ms){
    // returns 24 hour formatted time string
    // ms is time since start of day
    var dec = ms / 1000 / 60 / 60;
    var hr = Math.floor(dec);
    var minDec = dec - hr;
    var min = 60 * minDec;
    return [hr, zpad(min, 2)].join(":");
};