sunrise sunset times in c

Question

In my C application, I want to calculate sunrise/sunset times for a given date, latitude and longitude. i have been searching on the net but i can not find a working sample.

I tried to implement this sample: http://souptonuts.sourceforge.net/code/sunrise.c.html

But this sample didnt work correctly.

Is there a simple C source code or method which i can easly implement in my application?

Edit:
I implement the code on this link but it gave me the wrong sunset/sunrise values. Also i tried the Saul's link here but it gave me the wrong result either.
I have 41N, 28E location. When i try the codes, both sample says that sunrise value is aproximately 10:13 and sunset is 23:24. But the correct values are 06:06, 20:13.
I can not understand the problem.

Answer 1

Ten simple steps to follow to calculate sunrise / sunset time given the date, latitude and longitude

1. first calculate the day of the year

   N1 = floor(275 * month / 9) N2 = floor((month + 9) / 12) N3 = (1 + floor((year - 4 * floor(year / 4) + 2) / 3)) N = N1 - (N2 * N3) + day - 30

2. convert the longitude to hour value and calculate an approximate time

   lngHour = longitude / 15

   if rising time is desired: t = N + ((6 - lngHour) / 24) if setting time is desired: t = N + ((18 - lngHour) / 24)

3. calculate the Sun's mean anomaly

   M = (0.9856 * t) - 3.289

4. calculate the Sun's true longitude

   L = M + (1.916 * sin(M)) + (0.020 * sin(2 * M)) + 282.634 NOTE: L potentially needs to be adjusted into the range [0,360) by adding/subtracting 360

5a. calculate the Sun's right ascension

RA = atan(0.91764 * tan(L))
NOTE: RA potentially needs to be adjusted into the range [0,360) by adding/subtracting 360

5b. right ascension value needs to be in the same quadrant as L

Lquadrant  = (floor( L/90)) * 90
RAquadrant = (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

   sinDec = 0.39782 * sin(L) cosDec = cos(asin(sinDec))

7a. calculate the Sun's local hour angle

cosH = (cos(zenith) - (sinDec * sin(latitude))) / (cosDec * cos(latitude))

if (cosH >  1) 
  the sun never rises on this location (on the specified date)
if (cosH < -1)
  the sun never sets on this location (on the specified date)

7b. finish calculating H and convert into hours

if if rising time is desired:
  H = 360 - acos(cosH)
if setting time is desired:
  H = acos(cosH)

H = H / 15

8. calculate local mean time of rising/setting

   T = H + RA - (0.06571 * t) - 6.622

9. adjust back to UTC

   UT = T - lngHour NOTE: UT potentially needs to be adjusted into the range [0,24) by adding/subtracting 24

10. convert UT value to local time zone of latitude/longitude

    localT = UT + localOffset