# day.of.week

From chron v2.2-10
by Kurt Hornik

##### 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

```
julian(m, d, y, origin = c(month = 1, day = 1, year = 1970))
month.day.year(jul, origin = c(month = 1, day = 1, year = 1970))
leap.year(y)
day.of.week(month, day, year)
```

##### Arguments

- m
- vector of month numbers.
- d
- vector of day numbers.
- y
- 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)`

.

##### 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

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

*Documentation reproduced from package chron, version 2.2-10, License: GPL*

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