To cite package ‘solartime’ in publications use:

  Wutzler T (2024). _solartime: Utilities Dealing with Solar Time Such
  as Sun Position and Time of Sunrise_. R package version 0.0.4,
  <https://github.com/bgctw/solartime>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {solartime: Utilities Dealing with Solar Time Such as Sun Position and Time
of Sunrise},
    author = {Thomas Wutzler},
    year = {2024},
    note = {R package version 0.0.4},
    url = {https://github.com/bgctw/solartime},
  }