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));
```

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
- Saddle point approximation

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.

How to add leap_year changes to be made

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[12]={
31,28,31,30,31,30,31,31,30,31,30,31};
int leapYrDetect(){
if(local_year%4)
{
MNTH_DAYS[1]=28;
return(0);
}
else
{
MNTH_DAYS[1]=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);
}
}
```