R: Convert between Julian and Calendar Dates

day.of.week {chron} | R Documentation

## Convert between Julian and Calendar Dates

### Description

Utility functions to convert between Julian dates (numbers of days since an origin, by default 1970-01-01) and calendar dates given by year, month, and day within the month.

### Usage

    ## Default S3 method:
    julian(x, d, y, origin., ...)
    month.day.year(jul, origin.)
    leap.year(y)
    day.of.week(month, day, year)

### Arguments

`x, month` | vector of month numbers.
`d, day` | vector of day numbers.
`y, year` | vector of years.
`jul` | vector of Julian Dates, i.e., number of days since `origin.`.
`origin.` | vector specifying the origin as month, day, and year. If missing, it defaults to `getOption("chron.origin")` if this is non-null, otherwise `c(month = 1, day = 1, year = 1970)`.
`...` | further arguments to be passed to or from methods.

### Value

A vector of Julian dates (number of days since `origin.`) when `julian()` is called, or a list with members `month`, `day`, `year` corresponding to the input Julian dates if `month.day.year()` is called. `leap.year()` returns a logical vector indicating whether the corresponding year is a leap year. `day.of.week()` returns a number between 0 and 6 to specify day of the week–0 refers to Sunday.

These functions were taken from Becker, Chambers, and Wilks (1988), and were slightly modified to take `chron` and `dates` objects; some also take the extra argument `origin.`.

### See Also

`chron`, `dates`, `times`

### Examples

    julian(1, 1, 1970)
    # [1] 0
    unlist(month.day.year(0))
    # month   day  year
    #     1     1  1970

[Package chron version 2.3-53 Index]