Compute Sun Position, Sunlight Phases, Moon Position and Lunar Phase

Get sun position, sunlight phases (times for sunrise, sunset, dusk, etc.), moon position and lunar phase for the given location and time. Most calculations are based on the formulas given in Astronomy Answers articles about position of the sun and the planets : < https://www.aa.quae.nl/en/reken/zonpositie.html>.

suncalc

R package for calculating sun position, sunlight phases (times for sunrise, sunset, dusk, etc.), moon position, moon rise and set times, and lunar phase for the given location and time.

It is a full R implementation of the JavaScript library SunCalc, vectorized to work on large data. Most calculations are based on the formulas given in the Astronomy Answers articles about position of the sun and the planets.

Installation

# from CRAN
install.packages("suncalc")

# development version from GitHub
# install.packages("remotes")
remotes::install_github("datastorm-open/suncalc")

Usage

All functions return a data.frame, and share the same arguments:

• date, lat, lon: one or several dates, for a single location,
• or data: a data.frame with columns date, lat and lon, for several locations,
• keep: the variables to return (all by default),
• tz (getSunlightTimes() and getMoonTimes()): time zone of the results ("UTC" by default).

library(suncalc)

getSunlightTimes(date = as.Date("2026-06-21"), lat = 48.86, lon = 2.35, tz = "Europe/Paris",
                 keep = c("sunrise", "solarNoon", "sunset", "night"))
#         date   lat  lon             sunrise           solarNoon              sunset night
# 1 2026-06-21 48.86 2.35 2026-06-21 05:48:09 2026-06-21 13:53:35 2026-06-21 21:59:01  <NA>

# several locations
data <- data.frame(date = as.Date(c("2026-06-21", "2026-12-21")),
                   lat = c(48.86, 69.65),
                   lon = c(2.35, 18.96))
getSunlightTimes(data = data, keep = c("sunrise", "sunset", "night"), tz = "Europe/Paris")
#         date   lat   lon             sunrise              sunset               night
# 1 2026-06-21 48.86  2.35 2026-06-21 05:48:09 2026-06-21 21:59:01                <NA>
# 2 2026-12-21 69.65 18.96                <NA>                <NA> 2026-12-21 16:57:10

getMoonTimes(date = as.Date("2026-06-21"), lat = 48.86, lon = 2.35, tz = "Europe/Paris")
#         date   lat  lon                rise                 set alwaysUp alwaysDown
# 1 2026-06-21 48.86 2.35 2026-06-21 13:20:51 2026-06-21 01:28:57    FALSE      FALSE

getSunlightPosition(date = as.POSIXct("2026-06-21 12:00:00", tz = "Europe/Paris"), lat = 48.86, lon = 2.35)
#                  date   lat  lon  altitude    azimuth
# 1 2026-06-21 12:00:00 48.86 2.35 0.9823635 -0.8941455

getMoonIllumination(date = as.Date(c("2026-06-21", "2026-06-29")))
#         date  fraction     phase     angle
# 1 2026-06-21 0.3982594 0.2173872 -1.168386
# 2 2026-06-29 0.9894033 0.4671750 -1.940759

Times and NA values

getSunlightTimes() and getMoonTimes() return, for each requested day, the times of the events occurring that day in tz (from 00:00 to 24:00), whatever the system time zone.

A time is NA when the event doesn't occur that day:

• the sun doesn't reach the corresponding altitude: no night / nightEnd in summer at high latitudes (the sun never goes 18° below the horizon, as in Paris on June 21 above), no sunrise / sunset during polar day or polar night (Tromsø on December 21 above),
• the moon doesn't rise or set that day (about once a month, as moonrise and moonset are about 50 minutes later each day).

Reference

You can read about the different twilight phases in the Twilight article on Wikipedia.

Sunlight times: getSunlightTimes()

Each variable is a POSIXct in tz:

Sun position: getSunlightPosition()

• altitude: sun altitude above the horizon in radians, e.g. 0 at the horizon and pi/2 at the zenith (straight over your head)
• azimuth: sun azimuth in radians (direction along the horizon, measured from south to west), e.g. 0 is south and pi * 3/4 is northwest

Moon rise and set times: getMoonTimes()

• rise: moonrise time (POSIXct in tz)
• set: moonset time (POSIXct in tz)
• alwaysUp: TRUE if the moon never rises / sets and is always above the horizon during the day
• alwaysDown: TRUE if the moon is always below the horizon

Moon position: getMoonPosition()

• altitude: moon altitude above the horizon in radians
• azimuth: moon azimuth in radians
• distance: distance to moon in kilometers
• parallacticAngle: parallactic angle of the moon in radians

Moon illumination: getMoonIllumination()

• fraction: illuminated fraction of the moon; varies from 0.0 (new moon) to 1.0 (full moon)
• phase: moon phase; varies from 0.0 to 1.0, described below
• angle: midpoint angle in radians of the illuminated limb of the moon reckoned eastward from the north point of the disk; the moon is waxing if the angle is negative, and waning if positive

Moon phase value should be interpreted like this:

By subtracting the parallacticAngle from the angle one can get the zenith angle of the moon's bright limb (anticlockwise). The zenith angle can be used to draw the moon shape from the observer's perspective (e.g. moon lying on its back).

News

See NEWS.md for the changes of each version.