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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)
tibble::tibble(
  Gregorian = gregorian_date(1990, 2, 20) + 1:10,
  Date = as.Date(Gregorian),
  RD = as_rd(Gregorian),
  ISO = as_iso(Gregorian),
  Julian = as_julian(Gregorian),
  Roman = as_roman(Gregorian)
)
#> # A tibble: 10 × 6
#>      Gregorian Date           RD        ISO      Julian                    Roman
#>          <Gre> <date>       <RD>      <iso>       <Jul>                    <Rom>
#>  1 1990-Feb-21 1990-02-21 726519 1990-08-03 1990-Feb-08      1990-Feb-ad_vi_Ides
#>  2 1990-Feb-22 1990-02-22 726520 1990-08-04 1990-Feb-09       1990-Feb-ad_v_Ides
#>  3 1990-Feb-23 1990-02-23 726521 1990-08-05 1990-Feb-10      1990-Feb-ad_iv_Ides
#>  4 1990-Feb-24 1990-02-24 726522 1990-08-06 1990-Feb-11     1990-Feb-ad_iii_Ides
#>  5 1990-Feb-25 1990-02-25 726523 1990-08-07 1990-Feb-12     1990-Feb-pridie_Ides
#>  6 1990-Feb-26 1990-02-26 726524 1990-09-01 1990-Feb-13            1990-Feb-Ides
#>  7 1990-Feb-27 1990-02-27 726525 1990-09-02 1990-Feb-14  1990-Mar-ad_xvi_Kalends
#>  8 1990-Feb-28 1990-02-28 726526 1990-09-03 1990-Feb-15   1990-Mar-ad_xv_Kalends
#>  9 1990-Mar-01 1990-03-01 726527 1990-09-04 1990-Feb-16  1990-Mar-ad_xiv_Kalends
#> 10 1990-Mar-02 1990-03-02 726528 1990-09-05 1990-Feb-17 1990-Mar-ad_xiii_Kalends

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-May-26 2025-Jul-04 2025-Sep-01 2025-Nov-04 2025-Mar-09 2025-Nov-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-Apr-20 2025-Apr-20 2025-Apr-20 2025-Jun-08 2025-Nov-30 2025-Dec-25
#> [7] 2026-Jan-04 2026-Jan-07