Rata Die Conversion to and from Julian Years

Convenient functions for conversion from and to rata die.

Usage

fixed_from_julian(year, month, day)

fixed_to_julian(object)

Arguments

year

A numeric vector of years. If month and day are missing, decimal years are expected.

month

A numeric vector of months.

day

A numeric vector of days.

object

A RataDie object (see fixed()).

Value

• fixed_from_julian() returns a RataDie object.

• fixed_to_julian() returns a numeric vector of Julian years.

References

Reingold, E. M. and Dershowitz, N. (2018). Calendrical Calculations: The Ultimate Edition. Cambridge University Press. doi:10.1017/9781107415058 .

See also

Other fixed date tools: arithmetic, as_date(), as_decimal(), as_fixed(), as_year(), fixed(), fixed_gregorian, format(), pretty()

Author

N. Frerebeau

Examples

## R 1.0.0
(y <- fixed(year = 2000, month = 02, day = 29, calendar = CE()))
#> Rata die: number of days since 01-01-01 (Gregorian)
#> [1] 730179
as_date(y, calendar = CE())
#>   year month day
#> 1 2000     2  29
as_year(y, calendar = CE())
#> [1] 2000.161

## Create a vector of years BP (Gregorian)
## (every two years starting from 2000 BP)
(years <- seq(from = 2000, by = -2, length.out = 10))
#>  [1] 2000 1998 1996 1994 1992 1990 1988 1986 1984 1982
## Convert years to rata die
(rd <- fixed(years, calendar = BP()))
#> Rata die: number of days since 01-01-01 (Gregorian)
#>  [1] -18627 -17897 -17166 -16436 -15705 -14975 -14244 -13514 -12783 -12053
## Convert back to Gregorian years BP
as_year(rd, calendar = BP())
#>  [1] 2000 1998 1996 1994 1992 1990 1988 1986 1984 1982

## More convenient
(rd <- fixed_from_BP(years))
#> Rata die: number of days since 01-01-01 (Gregorian)
#>  [1] -18627 -17897 -17166 -16436 -15705 -14975 -14244 -13514 -12783 -12053
fixed_to_BP(rd)
#>  [1] 2000 1998 1996 1994 1992 1990 1988 1986 1984 1982