# SPA coding help

Dear all,

i am trying to implement modified version for SPA.
can some one tell me how to calculate day_of year .or else share algorithm

``````fraction of year=(2*pi/365)*(day_of year-1+((hour-12)/24));
``````

SPA, right.

• Simple power analysis
• Special Protection Area
• Self-Propelled Artillery

Or maybe, (and I hope this is it):

• Special pale ale

SPA means solar position algorithm.I wanted calculate day of year . Let me know how to calculte day of year

Is Google broken where you are?

You want to calculate "day of year", starting from what ? The month and the day ?

I can't think of any good reason why a solar position algorithm would even want "day of year"

michinyon:
You want to calculate "day of year", starting from what ? The month and the day ?

I can't think of any good reason why a solar position algorithm would even want "day of year"

Starting from month

Well I don’t know how you can calculate it, just from the month. From the day and the month, you would write something like this.

``````int daysPrior[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };

int dayOfYear ( int day, int month )    //  day is 1..31,  month is 1..12
{
if ( month < 1 || month > 12 ) return -1 ;
if ( day < 1 || day > 31 ) return -1 ;    // you can do a more thorough check if you want to

return ( daysPrior[month-1] + day );
}
``````

You would also need to fix this for a leap year. It is still not clear to me why a solar positioning algorithm
would even need this, unless it is implemented in an unnecessarily complicated way.

int leapPrior={0,31,60,91,121,152,182,213,244,274,305,335};

the below code has been worked , but What it will do during leap year.Where leap year date as above

michinyon:
Well I don’t know how you can calculate it, just from the month. From the day and the month, you would write something like this.

``````int daysPrior[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };
``````

int dayOfYear ( int day, int month )    //  day is 1…31,  month is 1…12
{
if ( month < 1 || month > 12 ) return -1 ;
if ( day < 1 || day > 31 ) return -1 ;    // you can do a more thorough check if you want to

return ( daysPrior[month-1] + day );
}

``````

You would also need to fix this for a leap year. It is still not clear to me why a solar positioning algorithm
would even need this, unless it is implemented in an unnecessarily complicated way.``````
``````static int MNTH_DAYS={
31,28,31,30,31,30,31,31,30,31,30,31};

int leapYrDetect(){

if(local_year%4)
{
MNTH_DAYS=28;
return(0);
}
else
{
MNTH_DAYS=29;
return(1);
}
}

int daysPrior[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };
int leapPrior[]={0,31,60,91,121,152,182,213,244,274,305,335};

int calcDayOfYear ( int dd, int mnth )    //  day is 1..31,  month is 1..12
{
int yr_day;
if(leapYrDetect()==0)
{
Serial.println("year is not leap year ");
if ( mnth < 1 || mnth > 12 ) return -1 ;
if ( dd < 1 || dd> 31 ) return -1 ;
yr_day= daysPrior[mnth-1] + dd ;

Serial.print("year of day is:");
Serial.println(yr_day);
return (yr_day);
}
if(leapYrDetect()==1)
{
Serial.println("leap year has detected ");
if ( mnth < 1 || mnth > 12 ) return -1 ;
if ( dd < 1 || dd> 31 ) return -1 ;
yr_day=leapPrior[mnth-1]+dd;
Serial.print("year of day is:");
Serial.println(yr_day);
return (yr_day);

}

}
``````