To cite package ‘suntools’ in publications use:

  Bivand R, Luque S (2024). _suntools: Calculate Sun Position, Sunrise,
  Sunset, Solar Noon and Twilight_. R package version 1.0.1,
  <https://CRAN.R-project.org/package=suntools>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {suntools: Calculate Sun Position, Sunrise, Sunset, Solar Noon and Twilight},
    author = {Roger Bivand and Sebastian Luque},
    year = {2024},
    note = {R package version 1.0.1},
    url = {https://CRAN.R-project.org/package=suntools},
  }