![Chronos](http://f.cl.ly/items/3W2Q0v2E3d0D0p412e1Z/7471443430_f127b84f8a_b.jpg)
# Chronos [![Build Status](https://travis-ci.org/nurugger07/chronos.png?branch=master)](https://travis-ci.org/nurugger07/chronos)
An Elixir library for handling dates. Chronos can be used in both production and testing to quickly
determine a date.
## Using
You can add Chronos as a dependency in your `mix.exs` file. Since it only requires Elixir and Erlang there are no other dependencies.
```elixir
def deps do
[ { :chronos, "~> 1.7.0" } ]
end
```
If you aren't using hex, add the a reference to the github repo.
``` elixir
def deps do
[ { :chronos, github: "nurugger07/chronos" } ]
end
```
Then run `mix deps.get` in the shell to fetch and compile the dependencies
To use the Chronos date features in your project you can import the Chronos module or call the functions directly.
```elixir
defmodule YourModule do
import Chronos
def get_today do
today
end
end
```
or you can call functions without the import
```elixir
defmodule YourModule do
def get_today do
Chronos.today
end
end
```
There are a number of functions to help with dates including below are some of the current APIs:
```iex
# yesterday without a date assumes you want the day before the current date
# current date is {2012, 12, 21}
iex> Chronos.yesterday
{2012, 12, 20}
iex> Chronos.tomorrow
{2012, 12, 22}
# epoch time can be return. If a time is not specified then midnight is assumed
iex> Chronos.epoch_time {2012, 12, 21}
1356048000
iex> Chronos.epoch_time {{2012, 12, 21}, {11, 11, 0}}
1356088260
```
You can find the date for days or weeks in the past or future:
```iex
iex> Chronos.days_ago(3)
{2012, 12, 18}
iex> Chronos.weeks_ago(5)
{2012, 11, 16}
```
## Use in Testing
Chronos is helpful in testing date based assertions because you can assign a default date or pass in a date to base the calculations on.
```elixir
defmodule TestingModule do
use Chronos, date: {2012, 12, 21}
end
```
If the date option is set the default date for all functions will be that date.
## Formatting Dates & Times
With the addition of Chronos.Formatter, you can begin to format date tuples to something more readable.
```iex
iex> Chronos.Formatter.strftime({2012, 12, 21}, "%Y-%m-%d")
"2012-12-21"
iex> Chronos.Formatter.strftime({2012, 12, 21}, "Presented on %m/%d/%Y")
"Presented on 12/21/2012"
```
Date/Times can also be formatted with the `strftime` function.
```iex
iex> Chronos.Formatter.strftime({{2012, 12, 21}, {13, 35, 44}}, "%Y-%m-%d %H:%M:%S")
"2012-12-21 13:35:44"
```
Chronos will also build valid http dates.
The default format is for RFC 1123:
``` iex
iex> Chronos.Formatter.http_date({{2012, 12, 21}, {13, 35, 44}})
"Fri, 21 Dec 2012 18:31:45 GMT"
```
However, there is also support for RFC 850 & ANSI C's asctime() format
``` iex
iex> Chronos.Formatter.http_date({{2012, 12, 21}, { 13, 31, 45 }}, :rfc850)
"Friday, 21-Dec-2012 18:31:45 GMT"
iex> Chronos.Formatter.http_date({{2012, 12, 21}, { 13, 31, 45 }}, :asctime)
"Fri Dec 21 18:31:45 2012"
```