How do I get the current time in Elm?

Question

I'm running elm-repl to play around with the language.

I'd like to see what the current time is. How would I do that? It doesn't appear to be possible with the current library. Why is that?

---

EDIT: I made a package to help with this. http://package.elm-lang.org/packages/z5h/time-app

This was asked around elm 0.15 - things are different in elm 0.17 & 0.18: see How do I get the current time in Elm 0.17/0.18?

Answer 1

Update for 0.19 It is not possible to get the current time using the standard library.. You need to use elm/time. As with 0.18, all you need is a command and Msg to handle the result

type Msg
    = OnTime Time.Posix 

getTime : Cmd Msg
getTime = 
    Task.perform OnTime Time.now 

Update for 0.18 This has got simpler again. Now all you need is a command and Msg to handle the result

type Msg
    = OnTime Time 

getTime : Cmd Msg
getTime = 
    Task.perform OnTime Time.now 

See this Ellie

Original answer

With 0.17, this got a whole lot easier. There is now a Task in the Time library. So for example, we now have:

Time.now
|> Task.Perform NoOp CurrentTime

Answer 2

You can use the Time package and/or the Date package.

Here's a contrived example which uses both:

import Signal
import Time exposing (every, second)
import Date exposing (year, hour, minute, second, fromTime)
import Graphics.Element exposing (show)

main =
  Signal.map currentTime (Time.every Time.second)

currentTime t =
  let date' = fromTime t
      hour' = toString (Date.hour date')
      minute' = toString (Date.minute date')
      second' = toString (Date.second date')
      year' = toString (year date')
      now = "The current time is: " ++ hour' ++ ":" ++ minute' ++ ":" ++ second'
  in 
      show now

Answer 3

To resolve my own question, I've created a variant of StartApp that includes a timestamp on each action.
So the update function has signature:
update : action -> Time -> model -> (model, Effects action)

The Gist is here. https://gist.github.com/z5h/41ca436679591b6c3e51

Answer 4

Elm 0.19

• https://elm-lang.org/examples/time
• https://elm-lang.org/examples/clock
• time https://ellie-app.com/3f6X2DW4cbma1
• Analog svg clock https://ellie-app.com/3dYXjr3bJNWa1

Below I set inital time as unix time start Time.millisToPosix 0, but you can set it to Nothing and later to Just time or pass it with Flag.

module Main exposing (main)

import Browser
import Html exposing (Html)
import Task
import Time exposing (Posix)


main : Program () Model Msg
main =
    Browser.element
        { init = \_ -> init
        , view = view
        , update = update
        , subscriptions = \_ -> Sub.none
        }



-- MODEL


type alias Model =
    { zone : Time.Zone
    , now : Posix
    }


init : ( Model, Cmd Msg )
init =
    ( Model Time.utc (Time.millisToPosix 0), Task.perform Zone Time.here )



-- UPDATE


type Msg
    = Zone Time.Zone
    | Now Posix


update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        Zone zone ->
            ( { model | zone = zone }, Task.perform Now Time.now )

        Now now ->
            ( { model | now = now }, Cmd.none )



-- VIEW


formatTime zone posix =
    (String.padLeft 2 '0' <| String.fromInt <| Time.toHour zone posix)
        ++ ":"
        ++ (String.padLeft 2 '0' <| String.fromInt <| Time.toMinute zone posix)
        ++ ":"
        ++ (String.padLeft 2 '0' <| String.fromInt <| Time.toSecond zone posix)


view : Model -> Html Msg
view model =
    Html.div []
        [ Html.text <| formatTime model.zone model.now
        ]

Answer 5

If you want the time as of program start you can do the following:

Now.elm

module Now where

import Native.Now

loadTime : Float
loadTime = Native.Now.loadTime

Native/Now.js

Elm.Native.Now = {};

Elm.Native.Now.make = function(localRuntime) {

  localRuntime.Native = localRuntime.Native || {};


  localRuntime.Native.Now = localRuntime.Native.Now || {};

  if (localRuntime.Native.Now.values) {
    return localRuntime.Native.Now.values;
  }

  var Result = Elm.Result.make(localRuntime);

  return localRuntime.Native.Now.values = {
    loadTime: (new window.Date).getTime()
  };

};

your code

programStart = Now.loadTime