main()
{
int year,month,day;
double lon, lat;
double daylen, civlen, nautlen, astrlen;
double rise, set, civ_start, civ_end, naut_start, naut_end,
astr_start, astr_end;
double daylen_int,daylen_frac; /* CWR */
int rs, civ, naut, astr;
int daylen_hours,daylen_min, gmtoff_hr; /* cwr */
double rise_int,rise_frac,set_int,set_frac;
int rise_hours,rise_min,set_hours,set_min;
time_t the_time; /* only need so can get time zone of local machine... */
struct tm *mylocal_time;
char buf[80];
/* get time and offset from GMT */
time(&the_time);
mylocal_time = localtime(&the_time);
gmtoff_hr = mylocal_time->tm_gmtoff/3600;
printf("Enter longitude and latitude in decimal degrees, i.e. -97.75 30.23\n");
printf("Hint: divide minutes by 60 to get decimal portion\n");
printf( "Longitude (+ is east) and latitude (+ is north) : " );
fgets(buf, 80, stdin);
sscanf(buf, "%lf %lf", &lon, &lat );
for(;;)
{
printf( "Input date ( yyyy mm dd ) (ctrl-C exits): " );
fgets(buf, 80, stdin);
sscanf(buf, "%d %d %d", &year, &month, &day );
daylen = day_length(year,month,day,lon,lat);
civlen = day_civil_twilight_length(year,month,day,lon,lat);
nautlen = day_nautical_twilight_length(year,month,day,lon,lat);
astrlen = day_astronomical_twilight_length(year,month,day,
lon,lat);
daylen_frac = modf(daylen,&daylen_int); /* daylen into int and fraction */
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( "Day length: %5.2f hours", daylen );
printf( "(%2d hours %2d min)\n", daylen_hours,daylen_min );
daylen_frac = modf(civlen,&daylen_int);
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( "With civil twilight %5.2f hours", civlen );
printf( "(%2d hours %2d min)\n", daylen_hours,daylen_min );
daylen_frac = modf(nautlen,&daylen_int);
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( "With nautical twilight %5.2f hours", nautlen );
printf( "(%2d hours %2d min)\n", daylen_hours,daylen_min );
daylen_frac = modf(astrlen,&daylen_int);
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( "With astronomical twilight %5.2f hours", astrlen );
printf( "(%2d hours %2d min)\n", daylen_hours,daylen_min );
daylen_frac = modf((civlen-daylen)/2.0,&daylen_int);
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( "Length of twilight: civil %5.2f hours",
(civlen-daylen)/2.0);
printf( "(%2d hours %2d min)\n", daylen_hours,daylen_min );
daylen_frac = modf((nautlen-daylen)/2.0,&daylen_int);
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( " nautical %5.2f hours",
(nautlen-daylen)/2.0);
printf( "(%2d hours %2d min)\n", daylen_hours,daylen_min );
daylen_frac = modf((astrlen-daylen)/2.0,&daylen_int);
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( " astronomical %5.2f hours",
(astrlen-daylen)/2.0);
printf( "(%2d hours %2d min)\n", daylen_hours,daylen_min );
rs = sun_rise_set ( year, month, day, lon, lat,
&rise, &set );
civ = civil_twilight ( year, month, day, lon, lat,
&civ_start, &civ_end );
naut = nautical_twilight ( year, month, day, lon, lat,
&naut_start, &naut_end );
astr = astronomical_twilight( year, month, day, lon, lat,
&astr_start, &astr_end );
daylen_frac = modf(((rise+set)/2.0)+gmtoff_hr ,&daylen_int);
daylen_hours = (int)daylen_int;
daylen_min = (int)(daylen_frac * 60);
printf( "Sun at south %5.2fh UT,%20d:%02d local\n", (rise+set)/2.0,daylen_hours,daylen_min);
switch( rs )
{
case 0:
/* add minutes and local. CWR*/
rise_frac = modf(rise+gmtoff_hr ,&rise_int);
rise_hours = (int)rise_int;
rise_min = (int)(rise_frac * 60);
set_frac = modf(set+gmtoff_hr ,&set_int);
set_hours = (int)set_int;
set_min = (int)(set_frac * 60);
printf( "Sun rises %5.2fh UT, sets %5.2fh UT;\n rises %02d:%02d, sets %02d:%02d local\n",
rise, set, rise_hours,rise_min,set_hours,set_min);
break;
case +1:
printf( "Sun above horizon\n" );
break;
case -1:
printf( "Sun below horizon\n" );
break;
}
switch( civ )
{
case 0:
rise_frac = modf(civ_start+gmtoff_hr ,&rise_int);
rise_hours = (int)rise_int;
rise_min = (int)(rise_frac * 60);
set_frac = modf(civ_end+gmtoff_hr ,&set_int);
set_hours = (int)set_int;
set_min = (int)(set_frac * 60);
printf( "Civil twilight starts %5.2fh, "
"ends %5.2fh UT;\n starts %02d:%02d, ends %02d:%02d local\n",
civ_start, civ_end,
rise_hours, rise_min, set_hours, set_min);
break;
case +1:
printf( "Never darker than civil twilight\n" );
break;
case -1:
printf( "Never as bright as civil twilight\n" );
break;
}
switch( naut )
{
case 0:
rise_frac = modf(naut_start+gmtoff_hr ,&rise_int);
rise_hours = (int)rise_int;
rise_min = (int)(rise_frac * 60);
set_frac = modf(naut_end+gmtoff_hr ,&set_int);
set_hours = (int)set_int;
set_min = (int)(set_frac * 60);
printf( "Nautical twilight starts %5.2fh, "
"ends %5.2fh UT;\n starts %02d:%02d, ends %02d:%02d local\n",
naut_start, naut_end,
rise_hours, rise_min, set_hours, set_min );
break;
case +1:
printf( "Never darker than nautical twilight\n" );
break;
case -1:
printf( "Never as bright as nautical twilight\n" );
break;
}
switch( astr )
{
case 0:
rise_frac = modf(astr_start+gmtoff_hr ,&rise_int);
rise_hours = (int)rise_int;
rise_min = (int)(rise_frac * 60);
set_frac = modf(astr_end+gmtoff_hr ,&set_int);
set_hours = (int)set_int;
set_min = (int)(set_frac * 60);
printf( "Astronomical twilight starts %5.2fh, "
"ends %5.2fh UT;\n starts %02d:%02d, ends %02d:%02d local\n",
astr_start, astr_end,
rise_hours, rise_min, set_hours, set_min );
break;
case +1:
printf( "Never darker than astronomical twilight\n" );
break;
case -1:
printf( "Never as bright as astronomical twilight\n" );
break;
}
return 0;
}
}
main()
{
int year,month,day;
double lon, lat;
double daylen, civlen, nautlen, astrlen;
double rise, set, civ_start, civ_end, naut_start, naut_end,
astr_start, astr_end;
int rs, civ, naut, astr;
char buf[80];
printf( "Longitude (+ is east) and latitude (+ is north) : " );
fgets(buf, 80, stdin);
sscanf(buf, "%lf %lf", &lon, &lat );
for(;;)
{
printf( "Input date ( yyyy mm dd ) (ctrl-C exits): " );
fgets(buf, 80, stdin);
sscanf(buf, "%d %d %d", &year, &month, &day );
daylen = day_length(year,month,day,lon,lat);
civlen = day_civil_twilight_length(year,month,day,lon,lat);
nautlen = day_nautical_twilight_length(year,month,day,lon,lat);
astrlen = day_astronomical_twilight_length(year,month,day,
lon,lat);
printf( "Day length: %5.2f hours\n", daylen );
printf( "With civil twilight %5.2f hours\n", civlen );
printf( "With nautical twilight %5.2f hours\n", nautlen );
printf( "With astronomical twilight %5.2f hours\n", astrlen );
printf( "Length of twilight: civil %5.2f hours\n",
(civlen-daylen)/2.0);
printf( " nautical %5.2f hours\n",
(nautlen-daylen)/2.0);
printf( " astronomical %5.2f hours\n",
(astrlen-daylen)/2.0);
rs = sun_rise_set ( year, month, day, lon, lat,
&rise, &set );
civ = civil_twilight ( year, month, day, lon, lat,
&civ_start, &civ_end );
naut = nautical_twilight ( year, month, day, lon, lat,
&naut_start, &naut_end );
astr = astronomical_twilight( year, month, day, lon, lat,
&astr_start, &astr_end );
printf( "Sun at south %5.2fh UT\n", (rise+set)/2.0 );
switch( rs )
{
case 0:
printf( "Sun rises %5.2fh UT, sets %5.2fh UT\n",
rise, set );
break;
case +1:
printf( "Sun above horizon\n" );
break;
case -1:
printf( "Sun below horizon\n" );
break;
}
switch( civ )
{
case 0:
printf( "Civil twilight starts %5.2fh, "
"ends %5.2fh UT\n", civ_start, civ_end );
break;
case +1:
printf( "Never darker than civil twilight\n" );
break;
case -1:
printf( "Never as bright as civil twilight\n" );
break;
}
switch( naut )
{
case 0:
printf( "Nautical twilight starts %5.2fh, "
"ends %5.2fh UT\n", naut_start, naut_end );
break;
case +1:
printf( "Never darker than nautical twilight\n" );
break;
case -1:
printf( "Never as bright as nautical twilight\n" );
break;
}
switch( astr )
{
case 0:
printf( "Astronomical twilight starts %5.2fh, "
"ends %5.2fh UT\n", astr_start, astr_end );
break;
case +1:
printf( "Never darker than astronomical twilight\n" );
break;
case -1:
printf( "Never as bright as astronomical twilight\n" );
break;
}
return 0;
}
}