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.

def deps do
  [ { :chronos, "~> 1.8.0" } ]
end

If you aren't using hex, add the a reference to the github repo.

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.

defmodule YourModule do

  import Chronos

  def get_today do
    today
  end
end

or you can call functions without the import

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:

# 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> 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.

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> 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> 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> 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> 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"