# day.of.week

##### Convert between Julian and Calendar Dates

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.

- Keywords
- chron

##### Usage

```
# S3 method for default
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

##### Examples

```
# NOT RUN {
julian(1, 1, 1970)
# [1] 0
unlist(month.day.year(0))
# month day year
# 1 1 1970
# }
```

*Documentation reproduced from package chron, version 2.3-55, License: GPL-2*