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.
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.
Numeric. Epoch year from which years are counted in Gregorian astronomical years (i.e. there is a "year zero").
Character. Full name of the era. Defaults to the value of
label
.
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).
Integer. Number of years represented by one unit, e.g. 1000
for ka. Default: 1.
Are years counted backwards (-1
) (the default) or forwards (1
)
from epoch
?
An object of class era
.
Other era definition functions:
eras()
Other era helper functions:
era_parameters
,
era_year_parameters
,
era_year
,
is_era_year()
,
is_era()
,
is_yr()
,
this_year()
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