User blog comment:Caesar213/Adding a clock on the wiki/@comment-3389940-20131013003400/@comment-5558012-20131013044412

Add this to MediaWiki:Common.js/countdownclock.js on your wiki

// ************************************************* // Experimental javascript countdown timer (Splarka) // Version 0.0.3 // ************************************************* function updatetimer(i) { var now = new Date; var then = timers[i].eventdate; var diff = count=Math.floor((then.getTime-now.getTime)/1000); // catch bad date strings if(isNaN(diff)) { timers[i].firstChild.nodeValue = '** ' + timers[i].eventdate + ' **' ; return; } // determine plus/minus if(diff<0) { diff = -diff; var tpm = 'T plus '; } else { var tpm = 'T minus '; }  // calculate the diff var left = (diff%60) + ' seconds'; diff=Math.floor(diff/60); if(diff > 0) left = (diff%60) + ' minutes ' + left; diff=Math.floor(diff/60); if(diff > 0) left = (diff%24) + ' hours ' + left; diff=Math.floor(diff/24); if(diff > 0) left = diff + ' days ' + left timers[i].firstChild.nodeValue = tpm + left; // a setInterval is more efficient, but calling setTimeout // makes errors break the script rather than infinitely recurse timeouts[i] = setTimeout('updatetimer(' + i + ')',1000); } function checktimers { //hide 'nocountdown' and show 'countdown' var nocountdowns = getElementsByClassName(document, 'span', 'nocountdown'); for(var i in nocountdowns) nocountdowns[i].style.display = 'none' var countdowns = getElementsByClassName(document, 'span', 'countdown'); for(var i in countdowns) countdowns[i].style.display = 'inline' //set up global objects timers and timeouts. timers = getElementsByClassName(document, 'span', 'countdowndate'); //global timeouts = new Array; // generic holder for the timeouts, global if(timers.length == 0) return; for(var i in timers) { timers[i].eventdate = new Date(timers[i].firstChild.nodeValue); updatetimer(i); //start it up   } } addOnloadHook(checktimers);

and import the page to your MediaWiki:Common.js page.

// ***************************** // Beginning of Script importing // ***************************** importArticle({    type: "script",     article: [         "MediaWiki:Common.js/countdownclock.js"     ] });