Trigger an Event by Browser Time and not setInterval()

[sniperman]

I know JavaScript has the capability to read the current time based on a user's computer clock.

I've currently set up a timer which updates a variable every 5 seconds

var gAge = 10;
var _gTimerEvents = [];

var teventid = addTimerEvent('IncAgeCB()', 5000);

function IncAgeCB()
{
	gAge = gAge + 10;
	alert(gAge);
}

function addTimerEvent(evtCB, durationMs)
{
	if (!evtCB || !durationMs)
		alert("Error: addTimerEvent:"+evtCB+","+durationMs);
		
	var te = setInterval(evtCB, durationMs);
	_gTimerEvents[te] = te;
	return te;
}

I also have a timer...

function updateClock ( )
{
  var currentTime = new Date ( );

  var currentHours = currentTime.getHours ( );
  var currentMinutes = currentTime.getMinutes ( );
  var currentSeconds = currentTime.getSeconds ( );

  // Pad the minutes and seconds with leading zeros, if required
  currentMinutes = ( currentMinutes < 10 ? "0" : "" ) + currentMinutes;
  currentSeconds = ( currentSeconds < 10 ? "0" : "" ) + currentSeconds;

  // Choose either "AM" or "PM" as appropriate
  var timeOfDay = ( currentHours < 12 ) ? "AM" : "PM";

  // Convert the hours component to 12-hour format if needed
  currentHours = ( currentHours > 12 ) ? currentHours - 12 : currentHours;

  // Convert an hours component of "0" to "12"
  currentHours = ( currentHours == 0 ) ? 12 : currentHours;

  // Compose the string for display
  var currentTimeString = currentHours + ":" + currentMinutes + ":" + currentSeconds + " " + timeOfDay;
  
}

One problem that this approach will encounter is that when a browser is refreshed it will lose its real time updates.

I would like to attempt to include a Cookie Session to store a timestamp as a variable and make the script rely more on using real browser time for a timestamp conditional rather than an interval or timer for a conditional.

I am having trouble in trying to run a timestamp subroutine.