float calcSun(int year, int month, int day, float latitude, float longitude, int sunset, float zenith)
{
int N1 = my_floor(275 * month / 9);
int N2 = my_floor((month + 9) / 12);
int N3 = (1 + my_floor((year - 4 * my_floor(year / 4) + 2) / 3));
int N = N1 - (N2 * N3) + day - 30;
float lngHour = longitude / 15;
float t;
if (!sunset)
{
//if rising time is desired:
t = N + ((6 - lngHour) / 24);
}
else
{
//if setting time is desired:
t = N + ((18 - lngHour) / 24);
}
float M = (0.9856 * t) - 3.289;
//calculate the Sun's true longitude
//L = M + (1.916 * sin(M)) + (0.020 * sin(2 * M)) + 282.634
float L = M + (1.916 * my_sin((M_PI/180.0f) * M)) + (0.020 * my_sin((M_PI/180.0f) * 2 * M)) + 282.634;
if (L<0) L+=360.0f;
if (L>360) L-=360.0f;
//5a. calculate the Sun's right ascension
//RA = atan(0.91764 * tan(L))
float RA = (180.0f/M_PI) * my_atan(0.91764 * my_tan((M_PI/180.0f) * L));
if (RA<0) RA+=360;
if (RA>360) RA-=360;
//5b. right ascension value needs to be in the same quadrant as L
float Lquadrant = (my_floor( L/90)) * 90;
float RAquadrant = (my_floor(RA/90)) * 90;
RA = RA + (Lquadrant - RAquadrant);
//5c. right ascension value needs to be converted into hours
RA = RA / 15;
//6. calculate the Sun's declination
float sinDec = 0.39782 * my_sin((M_PI/180.0f) * L);
float cosDec = my_cos(my_asin(sinDec));
//7a. calculate the Sun's local hour angle
//cosH = (cos(zenith) - (sinDec * sin(latitude))) / (cosDec * cos(latitude))
float cosH = (my_cos((M_PI/180.0f) * zenith) - (sinDec * my_sin((M_PI/180.0f) * latitude))) / (cosDec * my_cos((M_PI/180.0f) * latitude));
if (cosH > 1) {
return 0;
}
else if (cosH < -1)
{
return 0;
}
//7b. finish calculating H and convert into hours
float H;
if (!sunset)
{
//if rising time is desired:
H = 360 - (180.0f/M_PI) * my_acos(cosH);
}
else
{
//if setting time is desired:
H = (180.0f/M_PI) * my_acos(cosH);
}
H = H / 15;
//8. calculate local mean time of rising/setting
float T = H + RA - (0.06571 * t) - 6.622;
//9. adjust back to UTC
float UT = T - lngHour;
if (UT<0) {UT+=24;}
if (UT>24) {UT-=24;}
time_t now = time(NULL);
struct tm *tick_time = localtime(&now);
struct tm *gm_time = gmtime(&now);
int timezoneoffset = 60 * (60 * (24 * (tick_time->tm_wday - gm_time->tm_wday) + tick_time->tm_hour - gm_time->tm_hour) + tick_time->tm_min - gm_time->tm_min);
// Correct for transitions at the end of the week.
int SECONDS_IN_WEEK=604800;
if (timezoneoffset > SECONDS_IN_WEEK/2) timezoneoffset -= SECONDS_IN_WEEK;
if (timezoneoffset < -SECONDS_IN_WEEK/2) timezoneoffset += SECONDS_IN_WEEK;
timezoneoffset /= 3600;
APP_LOG(APP_LOG_LEVEL_DEBUG, "timezone offset %d", timezoneoffset);
APP_LOG(APP_LOG_LEVEL_DEBUG, "other timezone offset %d", (tick_time-gm_time));
// return UT+(tick_time-gm_time);
return UT;
}
/* not quite rint(), i.e. results not properly rounded to nearest-or-even */
float my_rint (float x)
{
float t = my_floor (my_fabs(x) + 0.5);
return (x < 0.0) ? -t : t;
}
float calcSun(int year, int month, int day, float latitude, float longitude, int sunset, float zenith)
{
int N1 = my_floor(275 * month / 9);
int N2 = my_floor((month + 9) / 12);
int N3 = (1 + my_floor((year - 4 * my_floor(year / 4) + 2) / 3));
int N = N1 - (N2 * N3) + day - 30;
float lngHour = longitude / 15;
float t;
if (!sunset)
{
//if rising time is desired:
t = N + ((6 - lngHour) / 24);
}
else
{
//if setting time is desired:
t = N + ((18 - lngHour) / 24);
}
float M = (0.9856 * t) - 3.289;
//calculate the Sun's true longitude
//L = M + (1.916 * sin(M)) + (0.020 * sin(2 * M)) + 282.634
float L = M + (1.916 * my_sin((M_PI/180.0f) * M)) + (0.020 * my_sin((M_PI/180.0f) * 2 * M)) + 282.634;
if (L<0) L+=360.0f;
if (L>360) L-=360.0f;
//5a. calculate the Sun's right ascension
//RA = atan(0.91764 * tan(L))
float RA = (180.0f/M_PI) * my_atan(0.91764 * my_tan((M_PI/180.0f) * L));
if (RA<0) RA+=360;
if (RA>360) RA-=360;
//5b. right ascension value needs to be in the same quadrant as L
float Lquadrant = (my_floor( L/90)) * 90;
float RAquadrant = (my_floor(RA/90)) * 90;
RA = RA + (Lquadrant - RAquadrant);
//5c. right ascension value needs to be converted into hours
RA = RA / 15;
//6. calculate the Sun's declination
float sinDec = 0.39782 * my_sin((M_PI/180.0f) * L);
float cosDec = my_cos(my_asin(sinDec));
//7a. calculate the Sun's local hour angle
//cosH = (cos(zenith) - (sinDec * sin(latitude))) / (cosDec * cos(latitude))
float cosH = (my_cos((M_PI/180.0f) * zenith) - (sinDec * my_sin((M_PI/180.0f) * latitude))) / (cosDec * my_cos((M_PI/180.0f) * latitude));
if (cosH > 1) { // no sunrise here on this day
return 100; // watchface won't draw indicator if this value is found
}
else if (cosH < -1){ // no sunset here on this day
return 100; // watchface won't draw indicator if this value is found
}
//7b. finish calculating H and convert into hours
float H;
if (!sunset)
{
//if rising time is desired:
H = 360 - (180.0f/M_PI) * my_acos(cosH);
}
else
{
//if setting time is desired:
H = (180.0f/M_PI) * my_acos(cosH);
}
H = H / 15;
//8. calculate local mean time of rising/setting
float T = H + RA - (0.06571 * t) - 6.622;
//9. adjust back to UTC
float UT = T - lngHour;
if (UT<0) {UT+=24;}
if (UT>24) {UT-=24;}
return UT;
}
