# ymd: Extract parts of various Date-Time Objects In tis: Time Indexes and Time Indexed Series

## Description

Extract the year, month or day, or all three (in yyyymmdd form), or the quarter, from a jul, ti, or from any object that `jul()` can handle.

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13``` ```ymd(x, ...) ## S3 method for class 'jul' ymd(x, ...) ## S3 method for class 'ssDate' ymd(x, ...) ## S3 method for class 'ti' ymd(x, offset = 1, ...) ## Default S3 method: ymd(x, ...) year(x, ...) quarter(x, ...) month(x, ...) day(x, ...) ```

## Arguments

 `x` a `ti` or `jul`, or something that `jul()` can create a `jul` object from. `...` other args to be passed to the method called by the generic function. `year`, `quarter`, `month`, `day` and `ymd.default` may pass these args to `as.Date`. `offset` for `ti` `x`, a number in the range [0,1] telling where in the period represented by `x` to find the day. 0 returns the first day of the period, while the default value 1 returns the last day of the period. For example, if `x` has `tif` = "wmonday" so that `x` represents a week ending on Monday, than any `offset` in the range [0, 1/7] will return the Tuesday of that week, while `offset` in the range (1/7, 2/7] will return the Wednesday of that week, `offset` in the range (6/7, 1] will return the Monday that ends the week, and so on.

## Details

`year`, `quarter`, `month` and `day` call `ymd`, and thus understand the same arguments as it does. The default implementation `ymd.default` passes it's arguments to a call to the function `jul`, so all of these functions work the same way that function does.

## Value

`ymd` and it's variants return numeric objects in yyyymmdd form.

`year`, `quarter`, `month` and `day` return numeric objects.

`ymd()` with no arguments returns today's yyyymmdd.

`jul`, `ti`, `as.Date`
 ```1 2 3 4 5 6 7``` ```ymd() ## today's date and time weekFromNow <- ymd(today() + 7) ## today() returns a daily ti year(jul(today())) month(Sys.time()) ## create a monthly tis (Time Indexed Series) aTis <- tis(0, start = c(2000, 1), end = c(2004, 12), freq = 12) ymd(ti(aTis)) ## the yyyymmdd dates of the observations ```