Calculate week number

I try to calculate the week number in a year (i.e. week #2 for the january 14 or week #11 for the march 16). I make this script for this:

list daysPerMonth;
integer year = 2008;
integer month = 1;
integer day = 13;

default {
state_entry() {
// Days per month
if (year % 4 == 0) { // If leap year
daysPerMonth = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
}
else {
daysPerMonth = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
}
// Total of days since year begining
float temp = 0.0;
integer i;
for (i = 0; i < month - 1; i++) { // Months increment
temp += llList2Integer(daysPerMonth, i); // Add number of days
}
// Add remaning days for the current month
temp += day;
// Convert to week
temp = (temp / 7.0) + 1;
llSay(0, "Week #" + (string)llFloor(temp));
}
}

This script works for the current year (200, but doesn't works for some months of 2009. If someone can help me...

The problem seems to be, that you don't count the fact, that the 1st of a month isn't always a monday...

I added another global var that indicates which weekday is the first day of the year...

This _might_ solve the problem - I only did a few tests, though...

Also, I wondered why you made your var «temp» a float - an integer would do fine (I changed this as well)

list daysPerMonth;
integer year = 2009;
integer month = 2;
integer day = 2;
integer startingDay = 4; // in 2009 the 1st of Januar is a Thursday -> the 4th day in this week

default {
state_entry() {
// Days per month
if (year % 4 == 0) { // If leap year
daysPerMonth = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
}
else {
daysPerMonth = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
}
// Total of days since year begining
integer temp = 0;
integer i;
for (i = 0; i < month - 1; i++) { // Months increment
temp += llList2Integer(daysPerMonth, i); // Add number of days
}
// Add remaning days for the current month
temp += day + startingDay; // Add the starting Day to the calculation
// Convert to week
temp = (temp / 7) + 1;
llSay(0, "Week #" + (string)llFloor(temp));
}
}

Im sorry but i dont have time to do the code just at the moment.

But you need to takei nto account two things.

1) Week one is the fisrst week that contaiins a Thursday, so 2010 week one starts on the fourth of January the other 3 days are week 53 of 2009. So 2009 is a 53 week year.

2) A leap year can not be calculated by dividing by 4, if i remember correctly it is a leap year if it is divisiable by 4, but not if it can also be divided by a hundred, unless it can be divided by a 1,000. So 2,000 was a leap year, but 2,400 will not be.

I will try and post some code later if no one beats me to it

Thanks a lot for those informations. I wait your code.

Code as promised, this one seems to work

integer getWeek(integer year, integer month, integer day) {

    //First calculate the Julien day number
    integer a = (14 - month) / 12;
    integer y = year + 4800 - a;
    integer m = month + 12 * a - 3;
    integer JD = day + (153 * m + 2) / 5 + y * 365 + y / 4 - y / 100 + y / 400 - 32045;

    //Then find the week number    
    integer d4 = (JD + 31741 - (JD % 7)) % 146097 % 36524 % 1461;
    integer L = d4 / 1460;
    integer d1 = ((d4 - L) % 365) + L;
    integer WeekNumber = d1 / 7 + 1;
    return WeekNumber;
}

edit: it can probably be optimised, it was a cut and paste job

Thanks to have help me Beverly! This script works good now. I don't think that I would make this script myself...

I take no credit for the maths i just converted it
the sourc is here
http://webexhibits.org/calendars/week.html

and my spelling is dreadfull