As far as I know there are in CRAN four R packages implementing the computations for the position of the sun and times of sunrise and sunset: ‘photobiology’, ‘fishmethods’, ‘solartime’ and ‘suncalc’.

The functions `sun_angles()`

and `day_night()`

from package ‘photobiology’ use Meeus equations as used by NOAA Solar Calculator https://www.esrl.noaa.gov/gmd/grad/solcalc/ which could be more precise than those in NOAA’s Excel worksheet which implement a simplified version of the Meeus equations especially for far into the past or far into the future calculations. The approximations based on Meuus equations are very good for years between 1800 and 2100 and results should still be sufficiently accurate for the range from -1000 to 3000 as long as the computation of Julian dates is correct. The Excel implementation is only valid for dates between 1901 and 2099 because of how Julian dates are computed in Excell.

Function `astrocalc4r()`

from package ‘fishmethods’ also implements Meeus equations (the authors work at NOAA). Function `computeSunPosition()`

from package ‘solartime’ uses unspecified equations and function `getSunlightPosition()`

is an R interface to the ‘suncalc.js’ library, part of the ‘SunCalc.net’ project <http://suncalc.net>.

Function `computeSunPosition()`

from package ‘solartime’ uses unspecified equations and function `getSunlightPosition()`

is an R interface to the ‘suncalc.js’ library, part of the ‘SunCalc.net’ project <http://suncalc.net>.