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..

Examples

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