calcal

The goal of calcal is to do calendrical calculations, based on the algorithms described in Reingold and Dershowitz (2018) Calendrical Calculations, 4th edition, Cambridge University Press.

It is a translation of the Lisp code produced by Reingold and Dershowitz for Calendrica 4.0.

Installation

You can install the development version of calcal from GitHub with:

# install.packages("pak")
pak::pak("robjhyndman/calcal")

Example

Dates in multiple calendars:

library(calcal)
#> 
#> Attaching package: 'calcal'
#> The following object is masked from 'package:base':
#> 
#>     julian
tibble::tibble(
  dates = seq(as.Date("1900-02-27"), length = 15, by = "1 day"),
  RD = as_rd(dates),
  Gregorian = as_gregorian(dates),
  Julian = as_julian(dates)
)
#> # A tibble: 15 × 4
#>    dates          RD  Gregorian     Julian
#>    <date>       <RD>      <Gre>      <Jul>
#>  1 1900-02-27 693653 1900-02-27 1900-02-15
#>  2 1900-02-28 693654 1900-02-28 1900-02-16
#>  3 1900-03-01 693655 1900-03-01 1900-02-17
#>  4 1900-03-02 693656 1900-03-02 1900-02-18
#>  5 1900-03-03 693657 1900-03-03 1900-02-19
#>  6 1900-03-04 693658 1900-03-04 1900-02-20
#>  7 1900-03-05 693659 1900-03-05 1900-02-21
#>  8 1900-03-06 693660 1900-03-06 1900-02-22
#>  9 1900-03-07 693661 1900-03-07 1900-02-23
#> 10 1900-03-08 693662 1900-03-08 1900-02-24
#> 11 1900-03-09 693663 1900-03-09 1900-02-25
#> 12 1900-03-10 693664 1900-03-10 1900-02-26
#> 13 1900-03-11 693665 1900-03-11 1900-02-27
#> 14 1900-03-12 693666 1900-03-12 1900-02-28
#> 15 1900-03-13 693667 1900-03-13 1900-02-29

Some US holidays

c(
  us_memorial_day(2025),
  us_independence_day(2025),
  us_labor_day(2025),
  us_election_day(2025),
  us_daylight_saving_start(2025),
  us_daylight_saving_end(2025)
)
#> <gregorian[6]>
#> [1] 2025-05-26 2025-07-04 2025-09-01 2025-11-04 2025-03-09 2025-11-02

Some Christian holidays

c(
  easter(2025),
  orthodox_easter(2025),
  alt_orthodox_easter(2025),
  pentecost(2025),
  advent(2025),
  christmas(2025),
  epiphany(2026),
  orthodox_christmas(2026)
)
#> <gregorian[8]>
#> [1] 2025-04-20 2025-04-20 2025-04-20 2025-06-08 2025-11-30 2025-12-25 2026-01-04
#> [8] 2026-01-07