This function takes takes a time interval in years and converts into days,
the unit commonly used in time operations in `R`

. The simple conversion
x * 365 does not work for large number of years, due to the presence of
leap years.

## Arguments

- x
the number of years of the interval

## Value

a `difftime`

object (in days)

## Examples

```
y2d(1)
#> Time difference of 365 days
y2d(1000)
#> Time difference of 365243 days
```