Create an era object

An era object defines the time scale associated with a vector of years (see yr()). era() returns an era object, either by looking up label in the standard eras defined in eras() or, if more than one argument is given, constructing a new definition with the specified parameters.

Usage

era(
  label = character(),
  epoch = NULL,
  name = label,
  unit = era_year("Gregorian"),
  scale = 1,
  direction = -1
)

Arguments

label

Character. If only one argument is given to era(), the abbreviated label of a standard era defined in eras(). Otherwise, the label to give to the era constructed using the following arguments.

epoch

Numeric. Epoch year from which years are counted in Gregorian astronomical years (i.e. there is a "year zero").

name

Character. Full name of the era. Defaults to the value of label.

unit

An era_year() object describing the name of the year unit and its average length in solar days. Defaults to a Gregorian year (365.2425 days).

scale

Integer. Number of years represented by one unit, e.g. 1000 for ka. Default: 1.

direction

Are years counted backwards (-1) (the default) or forwards (1) from epoch?

Value

An object of class era.

See also

Other era definition functions: eras()

Other era helper functions: era_parameters, era_year, era_year_parameters, is_era(), is_era_year(), is_yr(), this_year()

Examples

era("cal BP")
#> <era[1]>
#> [1] Before Present (cal BP): Gregorian years (365.2425 days), counted backwards from 1950

era("T.A.", epoch = -9021, name = "Third Age", direction = 1)
#> <era[1]>
#> [1] Third Age (T.A.): Gregorian years (365.2425 days), counted forwards from -9021