Discussion: PST/PDT function

On the wiki page for llGetDate, is a very simple function that returns the date in PST instead of GMT.

However, this function does not handle daylight savings time, nor does it handle the first day of any given month during the first 8 or so hours of the day.

I wrote a function that properly answers the date in PST/PDT form. It handles daylight savings, as well as the first of each month. It will work correctly for the next 5 years (up to the end of 2010).

Please let me know if this works for you or not, and if you have any problems post in the discussion thread for this.

- Jon

//////////////////////////////////////////////////
 //
 //		Answer today's date in PST/PDT
 //
 //		This function works for any date between Jan. 1, 2005
 //		and Dec. 31, 2010. It handles leap years as well as first
 //		day of month and first day of year rollbacks.
 //
 //		Based on the wiki GetPSTDate script.
 //
 //		Jon Marlin
 //
 
 string GetPSTDate () {
 
 	//		aprilDays is the day of the month of the first Sunday, from 2005 to 2010
 	list aprilDays = [3, 2, 1, 6, 5, 4];
 
 	//		octoberDays is the day of the month of the last Sunday, from 2005 to 2010
 	list octoberDays = [30, 29, 28, 26, 25, 31];
 
 	//		monthDays is the number of days in each month, not counting leap years
 	list monthDays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
 
 	string dateUTC = llGetDate ();
 
 	//		Parse the date string into individual year, month, and day integers
 	list dateList = llParseString2List (dateUTC, ["-"], []);
 	integer year = llList2Integer (dateList, 0);
 	integer month = llList2Integer (dateList, 1);
 	integer day = llList2Integer (dateList, 2);
 
 	//		Bounds check - the lists can't handle past 2010, so just return the UTC date for that case
 	if (year > 2010)
 		return (dateUTC);
 
 	//		Note - pstTime is actually pst/pdt time, depending on whether we are in DST or not
 	float pstTime = llGetWallclock ();
 
 	//		The standard non-DST offset is 8 hours, which is 28,800 seconds
 	integer offset = 28800;
 	integer yearOffset = year - 2005;
 
 	//		During daylight savings time, the time difference is 7 hours... Are we in DST?
 	//		First case - May to September, inclusive, is always DST
 	if (month > 4 && month < 10)
 		offset = 25200;
 
 	//		Second case - April
 	else if (month == 4) {
 		integer aprilDay = llList2Integer (aprilDays, yearOffset);
 		if (day > aprilDay)
 			offset = 25200;
 
 		//		After 2am PST it switches to DST
 		else if (day == aprilDay && pstTime > 7200.0)
 			offset = 25200;}
 
 	//		Third case - October
 	else if (month == 10) {
 		integer octoberDay = llList2Integer (octoberDays, yearOffset);
 		if (day < octoberDay)
 			offset = 25200;
 
 		//		After 2am PDT it switches back to PST
 		else if (day == octoberDay && pstTime < 7200)
 			offset = 25200;}
 
 	//		Handle the offset, and rollback (if it occurs)
 	if (llGetGMTclock () < offset) {
 		day = day - 1;
 		//		Handle month rollback
 		if (day == 0) {
 			month = month - 1;
 			//		Handle year rollback
 			if (month == 0) {
 				year = year - 1;
 				month = 12;
 				day = 31;}
 			else {
 		    	//		During a normal month rollback, the last day of the month varies
 				day = llList2Integer (monthDays, month - 1);
 
 		    	//		Between 2005 and 2010, 2008 is the only leap year
 				if (month == 2 && year == 2008)
 					day = 29;}}
 
 		//    	Between midnight and the time difference hour, answer the corrected date
 		return ((string)year + "-" + (string)month + "-" + (string)day);}
 	else
 		//    	If we're past the GMT - PST time difference for the day,
 		//		just answer the GMT date
 		return (dateUTC);
 }
 

Just a heads-up, the US intends to change the length of Daylight Saving Time beginning in 2007. It passed the House today, and should pass the Senate tomorrow. DST will begin earlier in the Spring, and end later in the Fall.

Washington Post Article

Since llGetWallClock() is correctly on PST/PDT, why doesn't subtracting it from llGetGMTClock() produce the correct result?

Well, because those functions return strings. I could probably parse the strings, and figure out from that, but this is how I did it...

- Jon

They return floats, not strings. The original function on the Wiki page correctly returns PST/PDT as far as I can see. Since llGetWallClock() returns time in seconds from midnight Pacific (regardless of Daylight Savings) subtracting it from llGetGMTClock() and checking whether it is negative produces the correct result.

Someone want to wiki this? I'm passing out here, and can't even be bothered to see if it's already been done. But by writing this, I'll probably remember. Isn't memory a funny thing?

</worst. post. evar.>

But if you have the correct PST in seconds, how to transfer it into a readable date like "2007-28-04 13:08:23"?

Funny, i have a syntax error (92,1)

on a two year old script? hardly surprising....

Gotta love necroposts.

If you're just compiling what's posted here, of course you'll get an error. This is a function, not a stand alone script. The compiler is just asking you where the rest of the script is.