Convert date-time to Julian Date (JD)

Convert regular calendar date-times to Julian Date.

Usage

datetime_to_jd(x)

Arguments

x

Date-time values as `POSIXct`, `POSIXlt`, or `Date`.

`Date` values are treated as midnight (`00:00:00`) in UTC.

Value

Numeric vector of Julian Date values (days).

Details

JD is a continuous day count used in astronomy.

The fractional part is time of day.

JD starts at noon, so midnight is shown as `.5`.

Uses ERFA with `scale = "UTC"`. Leap seconds are handled by ERFA.

See also

jd_to_datetime, mjd_to_datetime

Examples

old_accuracy <- getOption("digits")
options(digits = 11)

t <- as.POSIXct("2026-03-08 12:34:56", tz = "UTC")
datetime_to_jd(t)
#> [1] 2461108.0243

datetime_to_jd(as.Date("2026-03-08"))
#> [1] 2461107.5

options(digits = old_accuracy)