Javascript: restarting countdown timer doesn't work as I expect it to -

i making countdown timer should reseting , starting anew every 10 seconds. code came now:

function count(){     var end_date = new date().gettime()+10*1000;     setinterval(function(){       var current_date = new date().gettime();       var seconds_left = parseint((end_date - current_date) / 1000);       document.getelementbyid("countdown").innerhtml = seconds_left + " seconds ";     }, 1000); }  setinterval(function(){count()}, 10*1000); 

it supposed function follows:
+ set interval restart count() every 10 seconds.
+ count() defines end_date - date 10 seconds now.
+ count() sets interval restart every 1 second.
+ every 1 second seconds_left variable changed according how current_date changed respect end_date.
+ seconds_left becomes 0, setinterval step 1 fires , starts count() anew.

which step implementing wrong way? misunderstand functioning of setinterval()? here jsfiddle: http://jsfiddle.net/sy5stjun/ .

my guess each call in own new object , multiple instances of fighting ever 10 seconds.

using approach using date objects here possible re-write:

var tmr = null; var time;  function biginterval() {     clearinterval(tmr);     time = (new date()).valueof() + (10 * 1000);     smallinterval();     tmr = setinterval(smallinterval, 500); }  function smallinterval() {     var cur = (new date()).valueof();     var seconds_left = parseint((time - cur) / 1000);     document.getelementbyid("countdown").innerhtml = seconds_left + " seconds"; }  biginterval(); setinterval(biginterval, 10*1000); 

in above code i've updated small timer 500ms instead of 1000ms won't line system clock @ 1000 , visual jumps in numbers.

if exact timing isn't 100% important here possible shorter method:

var t = 10;  setinterval(function() {     document.getelementbyid("countdown").innerhtml = t + " seconds";     t--;     if (t <= 0) {         t = 10;     } }, 1000);