Unix2GMTorBST

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Revision as of 15:17, 9 December 2013 by Omei Qunhua (talk | contribs)
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Function: string Unix2GMTorBST(integer unixtime);

Convert a Unix time (time in seconds since 01-01-1970) to a date in the form Day-of-week + YYYY-MM-DD HH:MM + GMT or BST

Day-of-week will be a 3-letter day, and the string ends with "GMT" or "BST" as appropriate, with correct 1-hour adjustment for BST

e.g. Wed 2013-12-25 06:48 GMT

• integer unixtime a point in time represented by the number of seconds since 00:00 hours, Jan 1, 1970 UTC, e.g. a value returned by llGetUnixTime()

Specification

<lsl> // Omei Qunhua Jan 2013

list weekdays = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];

// Convert a Unix time in seconds to Day-of-week + YYYY-MM-DD HH:MM + GMT or BST string Unix2GMTorBST(integer insecs) {

   string str = Convert(insecs);
   if (llGetSubString(str, -3, -1) == "BST")   // if the result indicates BST ...
       str = Convert(insecs + 3600);            // ... Recompute at 1 hour later
   return str;

}

// This leap year test is correct for all years from 1901 to 2099 and hence is quite adequate for Unix Time computations integer LeapYear(integer year) {

   return !(year & 3);

}

integer DaysPerMonth(integer year, integer month) {

   if (month == 2)  	return 28 + LeapYear(year);
   return 30 + ( (month + (month > 7) ) & 1);   		// Odd months up to July, and even months after July, have 31 days

}

string Convert(integer insecs) {

   integer w; integer month; integer daysinyear;
   integer mins = insecs / 60;
   integer secs = insecs % 60;
   integer hours = mins / 60;
   mins = mins % 60;
   integer days = hours / 24;
   hours = hours % 24;
   integer DayOfWeek = (days + 4) % 7;    // 0=Sun thru 6=Sat
   integer years = 1970 +  4 * (days / 1461);
   days = days % 1461;                  // number of days into a 4-year cycle
   @loop;
   daysinyear = 365 + LeapYear(years);
   if (days >= daysinyear)
   {

days -= daysinyear; ++years; jump loop;

   }
   ++days;
   for (w = month = 0; days > w; )
   {

days -= w; w = DaysPerMonth(years, ++month);

   }
   string str =  ((string) years + "-" + llGetSubString ("0" + (string) month, -2, -1) + "-" + llGetSubString ("0" + (string) days, -2, -1) + " " +

llGetSubString ("0" + (string) hours, -2, -1) + ":" + llGetSubString ("0" + (string) mins, -2, -1) );

   string GMT_BST = " GMT";
   integer LastSunday = days - DayOfWeek;
   // BST is from the last Sunday in March to the last Sunday in October
   if (month == 3  && LastSunday > 24)     GMT_BST = " BST";
   if (month > 3)                          GMT_BST = " BST";
   if (month == 10 && LastSunday > 24)     GMT_BST = " GMT";
   if (month > 10)                         GMT_BST = " GMT";
   return (llList2String(weekdays, DayOfWeek) + " " + str + GMT_BST);

}

</lsl>

Example

<lsl> default {

   state_entry()
   {

llSay(0, Unix2GMTorBST(llGetUnixTime() ) );

   }

} </lsl>