# Counting: year-month-weekday

Source:`R/gregorian-year-month-weekday.R`

`year-month-weekday-count-between.Rd`

This is a year-month-weekday method for the `calendar_count_between()`

generic. It counts the number of `precision`

units between `start`

and `end`

(i.e., the number of years or months).

## Usage

```
# S3 method for clock_year_month_weekday
calendar_count_between(start, end, precision, ..., n = 1L)
```

## Arguments

- start, end
`[clock_year_month_weekday]`

A pair of year-month-weekday vectors. These will be recycled to their common size.

- precision
`[character(1)]`

One of:

`"year"`

`"quarter"`

`"month"`

- ...
These dots are for future extensions and must be empty.

- n
`[positive integer(1)]`

A single positive integer specifying a multiple of

`precision`

to use.

## Details

Remember that year-month-weekday is not comparable when it is `"day"`

precision or finer, so this method is only defined for `"year"`

and
`"month"`

precision year-month-weekday objects.

`"quarter"`

is equivalent to `"month"`

precision with `n`

set to `n * 3L`

.

## Examples

```
# Compute the number of months between two dates
x <- year_month_weekday(2001, 2)
y <- year_month_weekday(2021, c(1, 3))
calendar_count_between(x, y, "month")
#> [1] 239 241
# Remember that day precision or finer year-month-weekday objects
# are not comparable, so this won't work
x <- year_month_weekday(2001, 2, 1, 1)
try(calendar_count_between(x, x, "month"))
#> Error in vec_proxy_compare(x = x) :
#> 'year_month_weekday' types with a precision of >= 'day' cannot be trivially compared or ordered. Convert to 'year_month_day' to compare using day-of-month values.
```