Glue between Calendar and Ecto. For saving dates, times and datetimes in Ecto. Instead of using the Ecto types for Date, Time and DateTime, you can access the features of the Calendar library. With timezone awareness, parsing, and formatting functionality.

defp deps do
  [ {:calecto, "~> 0.3.8"}, ]
end

Here's how to display inserted_at and updated_at dates using the functionality of the Calendar library:

• Add :calecto to your deps in your mix.exs file (see above) and run mix deps.get

• If you are Phoenix you can add the line use Calecto.Model in the file web/web.ex in the model function definition like so:

def model do
  quote do
    use Ecto.Model
    use Calecto.Model, usec: true
  end
end

• An alternative method to adding the line in web/web.ex is the following: In your Ecto models, where you have a schema definition with a timestamps line, under the line that says use Ecto.Model add use Calecto.Model like so:

defmodule Weather do
  use Ecto.Model
  use Calecto.Model, usec: true

  schema "weather" do
    field :city, :string
    timestamps
  end
end

This means that your timestamps will be loaded as Calendar.DateTime structs instead of Ecto.DateTime structs and you can use the formatting functionality in Calendar.

• Format an inserted_at timestamp using Calendar:

@post.inserted_at |> Calendar.Strftime.strftime!("%A, %e %B %Y")

It will return for instance: Monday, 9 March 2015

There are other formatting functions. For instance: http timestamp, unix timestamp, RFC 3339 (ISO 8601). You can also shift the timestamp to another timezone in order to display what date and time it was in that particular timezone. See more in the Calendar documentation.

If you have a primitive type as listed below you can swap it for a Calecto type simply by adding the type to your Ecto schema.

If you have a datetime as a primitive type, you can use Calecto.NaiveDateTime or Calecto.DateTimeUTC. If you have a date as a primitive type, you can use Calecto.Date. If you have a time as a primitive type, you can use Calecto.Time.

Put the primitive type in your migrations and the Ecto type in your schema.

*) If you are using Postgres as a database you can also use the Calecto.DateTime type. This allows you to save any Calendar.DateTime struct. This is useful for saving for instance future times for meetings in a certain timezone. Even if timezone rules change, the "wall time" will stay the same. See the "DateTime with Postgres" heading below.

In your Ecto schema:

defmodule Weather do
  use Ecto.Model
  use Calecto.Model, usec: true

  schema "weather" do
    field :temperature,      :integer
    field :nice_date,        Calecto.Date
    field :nice_time,        Calecto.Time
    field :nice_datetime,    Calecto.DateTimeUTC
    field :another_datetime, Calecto.NaiveDateTime
    timestamps usec: true
    # the timestamps will be DateTimeUTC because of the `use Calecto.Model` line
  end
end

If you have a Calendar DateTime in the Etc/UTC timezone you can save it in Ecto as a DateTimeUTC.

Let's create a new DateTime to represent "now":

    iex> example_to_be_saved_in_db = Calendar.DateTime.now_utc
    %Calendar.DateTime{abbr: "UTC", day: 2, hour: 16, usec: 245828, min: 48,
     month: 3, sec: 19, std_off: 0, timezone: "Etc/UTC", utc_off: 0, year: 2015}

Another way of getting a DateTime is parsing JavaScript style milliseconds:

    iex> parsed_datetime = Calendar.DateTime.Parse.js_ms!("1425314899000")
    %Calendar.DateTime{abbr: "UTC", day: 2, hour: 16, usec: 0, min: 48, month: 3,
     sec: 19, std_off: 0, timezone: "Etc/UTC", utc_off: 0, year: 2015}

Since the field nice_datetime is of the DateTimeUTC type, we can save Calendar.DateTime structs there if they are in the Etc/UTC timezone:

    weather_struct_to_be_saved = %Weather{nice_datetime: parsed_datetime}

When a Calecto.DateTimeUTC type is received from the database it is loaded as a Calendar.DateTime struct. We can use the functions in Calendar to shift this UTC datetime to another time zone:

    iex> example_loaded_from_db |> Calendar.DateTime.shift_zone!("Europe/Copenhagen")
    %Calendar.DateTime{abbr: "CET", day: 2, hour: 17, usec: nil, min: 48,
      month: 3, sec: 19, std_off: 0, timezone: "Europe/Copenhagen", utc_off: 3600,
      year: 2015}

Or we could get the unix timestamp:

    iex> example_loaded_from_db |> Calendar.DateTime.Format.unix
    1425314899

Or format it via strftime:

    iex> example_loaded_from_db |> Calendar.Strftime.strftime!("The time is %T and it is %A.")
    "The time is 16:48:19 and it is Monday."

If you are using Postgres, you can save and load DateTime structs that are not in the Etc/UTC timezone. This requires that a special type is added to the database. By running the following command you can generate a migration that adds this type:

    mix calecto.add_type_migration

Then run the migration (mix ecto.migrate). This adds the calendar_datetime type to the Postgres database. In migrations you can use :calendar_datetime.

In the schemas you can use the type Calecto.DateTime for fields that have been created with :calendar_datetime type in migrations.

Documentation for Calecto is available at hexdocs.

More information about Calendar functionality in the Calendar documentation.

For existing users of Kalecto: Kalends has changed its name to Calendar. And because of this, Kalecto is now called Calecto with a C. It is not because of numerology, but because it makes more sense that both libraries start with the same letter 😉 To upgrade:

• In your code replace all instances of Kalecto with Calecto
• In your code replace all instances of :kalecto with :calecto
• In a similair fashion replace Kalends with Calendar and :kalends with :calendar
• In your mix.exs file make sure you are specifying a valid version of :calecto (see newest version above)