Sunrise and sunset times — sun_rise

Calculate the time of sunrise or sunset (or of the sun reaching a given angle below the horizon, such as twilight) for a vector of dates at a site, using the low-precision algorithm from the Almanac for Computers (accurate to about a minute or two).

Usage

sun_rise_set(
  date,
  latitude,
  longitude,
  timezone = "UTC",
  angle = 6,
  flag = c("rise", "set")
)

Arguments

date: dates of class Date.
latitude: latitude of site (deg), positive north, in [-90, 90].
longitude: longitude of site (deg), positive east, in [-180, 180].
timezone: Olson time zone name of the returned times, such as "UTC" (default) or "Australia/Brisbane". See OlsonNames().
angle: angle of the sun below the horizon (deg) at which the time is calculated. Use 0 for the geometric horizon, 0.833 for the conventional sunrise and sunset (refraction and solar disc), and 6, 12 or 18 for civil, nautical and astronomical twilight. Positive values are below the horizon. Default is 6.
flag: "rise" for the morning event or "set" for the evening event.

Value

A POSIXct vector in timezone, on the local calendar day of date. An error is raised if the sun does not reach angle on a date (for example polar day or night).

Examples

date <- as.Date("2021-06-21")
sun_rise_set(date, latitude = -27.5, longitude = 153, angle = 0)
#> [1] "2021-06-21 20:41:42 UTC"
sun_rise_set(date, latitude = -27.5, longitude = 153, timezone = "Australia/Brisbane",
             angle = 0, flag = "rise")
#> [1] "2021-06-21 06:41:42 AEST"
sun_rise_set(date, latitude = -27.5, longitude = 153, timezone = "Australia/Brisbane",
             angle = 0, flag = "set")
#> [1] "2021-06-21 16:57:27 AEST"