To cite package ‘calcal’ in publications use:

  Hyndman R (2026). _calcal: Calendrical Calculations_. R package
  version 1.0.4.9000, <https://github.com/robjhyndman/calcal>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {calcal: Calendrical Calculations},
    author = {Rob Hyndman},
    year = {2026},
    note = {R package version 1.0.4.9000},
    url = {https://github.com/robjhyndman/calcal},
  }