Get time components.

totalTime.js

/**
 * Get time components of milliseconds.
 */
var totalTime = function(milliseconds) {
  var aSecond = 1000;
  var aMinute = 60*aSecond;
  var anHour  = 60*aMinute;
  var aDay    = 24*anHour;
  var aWeek   = 7*aDay;
  var aYear   = 365.25*aDay;
  var mathFn  = (milliseconds<0?'ceil':'floor');

  this.years = function() { return Math[mathFn](milliseconds / aYear); };
  this.days = function() { return Math[mathFn]((milliseconds % aYear) / aDay); };
  this.hours = function() { return Math[mathFn](((milliseconds % aYear) % aDay) / anHour); };
  this.minutes = function() { return Math[mathFn]((((milliseconds % aYear) % aDay) % anHour) / aMinute); };
  this.seconds = function() { return Math[mathFn](((((milliseconds % aYear) % aDay) % anHour) % aMinute) / aSecond); };
  this.milliseconds = function() { return Math[mathFn](((((milliseconds % aYear) % aDay) % anHour) % aMinute) % aSecond); };
  this.totalWeeks = function() { return Math[mathFn](milliseconds / aWeek); };
  this.totalDays = function() { return Math[mathFn](milliseconds / aDay); };
  this.totalHours = function() { return Math[mathFn](milliseconds / anHour); };
  this.totalMinutes = function() { return Math[mathFn](milliseconds / aMinute); };
  this.totalSeconds = function() { return Math[mathFn](milliseconds / aSecond); };
}

toUTCWeekMilliseconds.js

/**
 * Get the number of milliseconds since Sunday at 00:00:00 [UTC].
 */
Date.prototype.toUTCWeekMilliseconds = function() {
  return (this.getUTCDay()*24*60*60*1000) // Days
    + (this.getUTCHours()*60*60*1000)     // Hours
    + (this.getUTCMinutes()*60*1000)      // Minutes
    + (this.getUTCSeconds()*1000)         // Seconds
    + this.getUTCMilliseconds();          // Milliseconds
}

Instead of the totalTime class, you can also use the Moment.js library which can handle durations.