# week

##### Get/set weeks component of a date-time

`week()`

returns the number of complete seven day periods that have
occurred between the date and January 1st, plus one.

`isoweek()`

returns the week as it would appear in the ISO 8601
system, which uses a reoccurring leap week.

`epiweek()`

is the US CDC version of epidemiological week. It
follows same rules as `isoweek()`

but starts on Sunday. In other parts of
the world the convention is to start epidemiological weeks on Monday,
which is the same as `isoweek`

.

##### Usage

`week(x)`week(x) <- value

isoweek(x)

epiweek(x)

##### Arguments

- x
a date-time object. Must be a POSIXct, POSIXlt, Date, chron, yearmon, yearqtr, zoo, zooreg, timeDate, xts, its, ti, jul, timeSeries, or fts object.

- value
a numeric object

##### Value

the weeks element of x as an integer number

##### References

http://en.wikipedia.org/wiki/ISO_week_date http://www.cmmcp.org/epiweek.htm

##### See Also

##### Examples

```
# NOT RUN {
x <- ymd("2012-03-26")
week(x)
week(x) <- 1
week(x) <- 54
week(x) > 3
# }
```

*Documentation reproduced from package lubridate, version 1.7.4, License: GPL (>= 2)*