Last updated: September 4th 2008.
This script was initially written as a cooking type of timer for recipes. You can set the hours, minutes and seconds. When you hit the start button it starts the timer until it reaches zero, then you'll get an alert telling you the time is up. Feel free to use this in any way you see fit. There may or may not be some bugs in this script but so far it seems to run pretty smooth for me.

Demo:

00:00:00
Hrs	Min	Sec
:	:
[+] [-]	[+] [-]	+ -]

Simply copy/paste the code below into the BODY of your webpage where you want the timer to appear.
Click Here to Copy contents to your Clipboard
<script language=javascript> <!--// //Javascript Countdown Timer. //set the amount of time click //start timer and the clock will //count down until it reaches zero //Jason Russo http://thescriptcenter.com var message = "Complete."; //do not edit below this line.// var parselimit=0; var st=0; var limit,curhour,curmin,cursec; function set_limit(strtstop) { //prevent multiple settimeouts if(st) { clearTimeout(st); } if(document.getElementById("pause").value == 1) { limit=document.getElementById("show_timer").innerHTML; } else { limit=document.getElementById("hours").value + ":" + document.getElementById("min").value + ":" + document.getElementById("sec").value; } parselimit=limit.split(":"); // take the minutes x 60 add it to the seconds; parselimit=parselimit[0]*3600+parselimit[1]*60+parselimit[2]*1; //exit if timer wasn't set. // if(parselimit <= 0) { return; } if(strtstop == 1) { clearTimeout(st); } else { st = setTimeout("begintimer()",1000); } } function begintimer(){ if (parselimit==1) { //ding ding ding document.getElementById("show_timer").innerHTML = message; alert(message);return; } else{ parselimit-=1; curhour=Math.floor(parselimit/3600); //alert(parselimit) /* greater than an hour divide by 60 but subtract the hours. */ if(parselimit > 3600) { //first convert hours back into seconds curmin = curhour * 3600; //subtract that from total to get minutes left. curmin = parselimit - curmin; curmin = Math.floor(curmin/60); //alert(curmin); } else { curmin = Math.floor(parselimit/60); } cursec=parselimit%60; } curmin += ""; if(curmin.length == 1 || curmin==9) { curmin = "0" + curmin; } cursec += ""; //alert(cursec); if(cursec.length == 1 || cursec==9) { cursec = "0" + cursec; } curtime = curhour + ":" + curmin + ":" + cursec; //alert(document.getElementById("show_timer").innerHTML); document.getElementById("show_timer").innerHTML = curtime; st=setTimeout("begintimer()",1000); } function add_time_clock(x,frmelm) { var ter = document.getElementById(frmelm).value; /* add time */ if(x==1) { ter = eval(ter) + 1; //if greater than 60 go to zero. i'm maxing out the hours at 60 too. if(ter >= 60) { ter='00'; } } else { /* subtract time */ ter = eval(ter)-1; //if greater than 60 go to zero. i'm maxing out the hours at 60 too. if(ter <= 0) { ter = '00'; } } ter = "" + ter; if(ter.length == 1) { ter = "0" + ter; } document.getElementById(frmelm).value = ter; } function rset_tmr() { document.getElementById('show_timer').innerHTML = "00:00:00"; document.getElementById('pause').value=0; } function show_hide(div) { if(document.getElementById(div).style.display=='none') { document.getElementById(div).style.display=''; } else { document.getElementById(div).style.display='none'; } } //--> </script> <div id=set_timer style=""> <input type=hidden id=pause value=0> <BR> <table border=1 cellspacing=0 bordercolor="#000000"><TR> <TD colspan=3 align=center height=25><B><span id=show_timer>00:00:00</span></B> </TD></TR><TR><TD>Hrs</TD><TD>Min</TD><TD>Sec</TD></TR><TR><TD> <input type=text id=hours size=1 maxlength=2 value="00">:</TD><TD><input type=text id=min size=1 maxlength=2 value=00>:</TD><TD> <input type=text id=sec value="00" maxlength=2 size=2></TD></TR> <TR><TD>[<a href="javascript:add_time_clock('1','hours')">+</A>] [<a href="javascript:add_time_clock('2','hours')">-</A>]</TD><TD>[<a href="javascript:add_time_clock('1','min')">+</A>] [<a href="javascript:add_time_clock('2','min')">-</A>]</TD><TD><a href="javascript:add_time_clock('1','sec')">+</A> <a href="javascript:add_time_clock('2','sec')">-</A>]</TD></TR> <TR><TD colspan=3 align=center> <input type=button value="Start" onclick="set_limit()"> <input type=button value="Pause" onclick="set_limit('1'),document.getElementById('pause').value=1"> <input type=button value="Reset" onclick="rset_tmr()"></TD></TR> </TABLE><BR><BR> </div>