# Leap

Given a year, report if it is a leap year.

The tricky thing here is that a leap year in the Gregorian calendar occurs:

```text
on every year that is evenly divisible by 4
  except every year that is evenly divisible by 100
    unless the year is also evenly divisible by 400
```

For example, 1997 is not a leap year, but 1996 is.  1900 is not a leap
year, but 2000 is.

## Notes

Though our exercise adopts some very simple rules, there is more to
learn!

For a delightful, four minute explanation of the whole leap year
phenomenon, go watch [this youtube video][video].

[video]: http://www.youtube.com/watch?v=xX96xng7sAE


Run the tests with:

```bash
bats leap_test.sh
```

After the first test(s) pass, continue by commenting out or removing the
`[[ $BATS_RUN_SKIPPED == true ]] || skip` 
annotations prepending other tests.

To run all tests, including the ones with `skip` annotations, run:

```bash
BATS_RUN_SKIPPED=true bats leap_test.sh
```

## Source

JavaRanch Cattle Drive, exercise 3 [http://www.javaranch.com/leap.jsp](http://www.javaranch.com/leap.jsp)


## External utilities
`Bash` is a language to write "scripts" -- programs that can call
external tools, such as
[`sed`](https://www.gnu.org/software/sed/),
[`awk`](https://www.gnu.org/software/gawk/),
[`date`](https://www.gnu.org/software/coreutils/manual/html_node/date-invocation.html)
and even programs written in other programming languages, 
like [`Python`](https://www.python.org/).
This track does not restrict the usage of these utilities, and as long
as your solution is portable between systems and does not require
installation of third party applications, feel free to use them to solve
the exercise.

For an extra challenge, if you would like to have a better understanding
of the language, try to re-implement the solution in pure `Bash`,
without using any external tools. Note that there are some types of
problems that bash cannot solve, such as performing floating point
arithmetic and manipulating dates: for those, you must call out to an
external tool.

## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others
have completed the exercise.