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Adapter for the Calendar library in Ecto
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Library originally made for older Ecto versions

This was made before Ecto had native support for built in Elixir Calendar types. If Ecto 2.1 and newer is used, Calecto should only be used for the Calecto.DateTime type, which is meant for DateTimes that are not UTC only. This type is specific to Postgres. Except for Calecto.DateTime the other types have equivalent built in types in Ecto 2.1.


Library to make it easy to use Calendar and Ecto together. 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.

For use with Elixir 1.3+ and Ecto 2.1+ add the following version to your deps:

defp deps do
  [ {:calecto, "~> 0.17.0"}, ]

If you use a Calendar version earlier than 0.16, use Calecto version ~> 0.6.1 If you use an Ecto version earlier than 2.1, use Calecto version ~> 0.16.0

Super quick way to get started

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 using Phoenix

  • If you are using Phoenix you can add the line use Calecto.Schema in the file web/web.ex in the model function definition like so:
def model do
  quote do
    use Ecto.Schema
    use Calecto.Schema, usec: true

    # ...

If you are not using Phoenix

  • 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.Schema add use Calecto.Schema like so:
defmodule Weather do
  use Ecto.Schema
  use Calecto.Schema, usec: true

  schema "weather" do
    field :city, :string

Formatting timestamps

This means that your timestamps will be loaded as DateTime structs instead of Ecto.DateTime structs. 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.

The types

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.

Except for Calecto.DateTime only use the types starting with Calecto with Ecto version older than 2.1. For Ecto 2.1 and higher use the types that are built into Ecto 2.1 - shown in the second column.

Primitive type Ecto 2.1+ schema type Legacy Ecto schema type Equivalent Calendar type
Used in migrations Used in schemas Used in schemas Type returned from db
:date :date Calecto.Date Date
:time :time Calecto.Time Time
:utc_datetime :utc_datetime Calecto.DateTimeUTC DateTime
:naive_datetime :naive_datetime Calecto.NaiveDateTime NaiveDateTime
:calendar_datetime Calecto.DateTime* Calecto.DateTime* DateTime

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.

Example usage

In your Ecto schema:

defmodule Weather do
  use Ecto.Schema
  use Calecto.Schema, 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.Schema` line

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 = DateTime.utc_now
    %DateTime{calendar: Calendar.ISO, day: 30, hour: 15, microsecond: {46167, 6},
    minute: 47, month: 6, second: 15, std_offset: 0, time_zone: "Etc/UTC",
    utc_offset: 0, year: 2016, zone_abbr: "UTC"}

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

    iex> parsed_datetime = Calendar.DateTime.Parse.js_ms!("1425314899000")
    %DateTime{calendar: Calendar.ISO, day: 2, hour: 16, microsecond: {0, 3},
    minute: 48, month: 3, second: 19, std_offset: 0, time_zone: "Etc/UTC",
    utc_offset: 0, year: 2015, zone_abbr: "UTC"}

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}

The DateTime struct returned from the database can be used with Calendar.DateTime functions. We could for instance 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")
    %DateTime{calendar: Calendar.ISO, day: 2, hour: 17, microsecond: {0, 3},
    minute: 48, month: 3, second: 19, std_offset: 0, time_zone: "Europe/Copenhagen",
    utc_offset: 3600, year: 2015, zone_abbr: "CET"}

Or we could get the unix timestamp:

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

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."

The are many more possiblities with Calendar for formatting, parsing etc. Look at the Calendar documentation for a detailed description.

DateTime with Postgres

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.

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