ServerDate to JavaScript

ServerDate to JavaScript (A free script from MRE Software)

My server time:
Your system:

I have a page on a website with a calendar JavaScript which posts upcoming dates. I wanted to control the initialization date on this script from the server as opposed to using the client computer's local date. I went looking around on the web for a "quick fix" but what I found involved either renaming the page with a php or shtml extension and using php or a server side include. Since this just happened to be the long established home page to my site, I didn't want to change the name. After some thought, I came up with a solution to the problem. Since I have used so many other scripts and ideas from the web, I thought I would give one back. A little more explanation... This time business is a "can of worms". What this actually does is set a JavaScript variable, on the client's machine, to the actual time on the webserver. This variable is expressed as a local time. Confused? Maybe an example will help. Example: It is 07:21:00 on my server located in lets say Chicago (central time). A user in San Francisco (pacific time) brings up my website. When this routine is called, the variable servertimeOBJ will return the time in Chicago (+2 hours ahead of SF) ServertimeOBJ will be 07:21:00 with the appropriate date etc. as required. If I use servertimeOBJ to adjust my scripts, the SF user will see dates/times in Chicago. Lets say I have a clock on the site...When the SF user pulls up the site the clock will display 07:21:00 to him even though it is 05:21:00 at his location. He sees Chicago time. This script can be edited, modified, adjusted, whatever to suit your exact needs, hopefully it demonstrates some useful concepts. First of all you will need to be able to run CGI programs on your server as you can't query the date from it without this ability. In my case I used a small PHP program to get the date and pass it back to the page via a JavaScript variable. <?php // Copyright 2007 Emery Wooten - www.mresoftware.com // Name this program servertime.php and place it in the main part of your site. // Change mode to executable... chmod 755 // // This program is called from Javascript. // It gets the server time and date and sets a JavaScript variable. // The variable servertimeOBJ, is set to the server time. // This should be called before any JavaScripts that use the date. // // Example call in html page: // <script language="JavaScript" src="http://yoursite.com/servertime.php"></script> // The statement above can even be placed in the <head> section of your page. // // Supress errors error_reporting(0); $myTimeZone = -6; //Edit for your timezone EST=-5 CST=-6 MST=-7 PST =-8 etc. $daylight = 1; // Set to 1 if you observe daylight savings time, 0 if not // $myoffs = ($myTimeZone * 3600) - date("Z"); //number of seconds my zone - the server differs from UTC $now = time() + $myoffs; // Get my standard time & date off of UTC if ($daylight){ $myoffs = $myoffs + DST($now)3600; // Correct for DST if date is in range } // Get server date $mydate = date("U"); // Adjust offsets for local machine print "var tzoffset = $myoffs + (new Date().getTimezoneOffset()60);"; // Set JavaScript variable to your server time as seen from client machine's location. print "var servertimeOBJ=new Date(($mydate+tzoffset)1000);"; //This function determines if the date is during daylight savings time in the USA function DST ($date_ck){ $DST_begin = OCR(2,0,3,date("Y",$date_ck)); //Find 2nd Sunday in March $DST_end = OCR(1,0,11,date("Y",$date_ck)); //Find 1st Sunday in November if (($date_ck >= $DST_begin) && ($date_ck + 3600 <= $DST_end)){ return (1); // return one if DST is in effect on this date } else{ return (0); // return zero if DST is not in effect on this date } } // // this function finds the requested (1st 2nd etc.)occurance of a day (0=Sunday - 6=Saturday) in the month (1-12) and year (xxxx) requested function OCR ($occur,$day,$month,$year){ $occur--; //Decrement so multiplication works later if ($occur < 0){$occur = 0;} //Limit to positive interger if ($occur > 4){$occur = 4;} //Limit to 5th occurance in month $dom = 1; $Ocr_date = mktime (2,0,0,$month,$dom,$year); //Start at 2:00am on 1st of the month while (date("w",$Ocr_date) != $day){ //Check to see if it is the day wanted $dom++; //Increment the day of the month $Ocr_date = mktime (2,0,0,$month,$dom,$year); //Update the date } $dom = $dom + ($occur7); //Add 7 times the occurance to the first occurance to get our date if ($dom > date("t")){$dom = $dom - 7;} // If past the end of the month, subtract 7 days (finds last occurance in month) $Ocr_date = mktime (2,0,0,$month,$dom,$year); //Update the date return $Ocr_date; //return the date found } ?> Once you have servertime.php installed on your site, you will need to call it from your html page. The example included in the PHP code above is all you need to do. Of course you should replace "yoursite.com" with the URL of your website. Call this BEFORE you call any other JavaScripts that need the date/time variable. In the example below I have a complete html page which calls the servertime.php file in the head section and then runs a JavaScript which uses it print the time on the server. You can take this basic code and incorporate it into your own scripts. <html> <head> <title>ServerDate to JavaScript</title> <script language="JavaScript" src="http://www.yoursite.com/servertime.php"></script> </head> <body> <script language "JavaScript"> // This short script gets the date/time from the server and prints it var deltaD = (servertimeOBJ.getTime())-(new Date().getTime()); var clientDate = new Date(); var serverdate = new Date(clientDate.getTime()+deltaD); // At this point serverdate can be used for all date/time references in the rest of the script. // The math above corrects its value for the the client's local time offset. var hours=serverdate.getHours(); var minutes=serverdate.getMinutes(); var seconds=serverdate.getSeconds(); var dn="AM"; if (hours>=12){dn="PM";} if (hours>12){hours=hours-12;} if (hours==0){hours=12;} if (minutes<=9){minutes="0"+minutes;} var cdate=hours+":"+minutes+" "+dn; document.write(cdate); </script> </body> </html>



The date and time in red at the top of this page was produced using the methods detailed herein. If you change your local computer date by say two months, change the time zone, daylight time, whatever, so that it is wrong, and refresh this page you will see that the red date/time remains the same and displays the date and time from the server, not from your local system. You can view the source code of this page for more details... This is a standard html page and uses no Server Side Includes. To download the JavaScript code that uses the servertimeOBJ variable and actually displays the ticking times at the top of this page, click here.

USE AT YOUR OWN RISK!
Questions / Comments? Email me.
Submitted in 2005