The new calendar types in Elixir 1.3

Elixir 1.3 adds new built-in types for date and time.

Hear about the considerations behind them and how they can improve the quality of your data and software.

When should you use a NaiveDateTime instead of a DateTime? Find out the what best practices are for all the new types. Be it with Ecto, with Phoenix or in Elixir in general.

Transcript

1. Calendar types in
   Elixir 1.3
   ElixirConf 2016
   

   View Slide

2. Lau Taarnskov
   Software developer
   Open source contributor. Creator of
   Calendar for Elixir and tzdata
   Blog: creativedeletion.com
   Twitter: @laut
   Github: lau
   

   View Slide

3. Lau Taarnskov - twitter: @LauT
   What is a type?
   

   View Slide

4. Lau Taarnskov - twitter: @LauT
   Why have types?
   

   View Slide

5. Lau Taarnskov - twitter: @LauT
   iex(1)> 5/2
   2.5
   

   View Slide

6. Lau Taarnskov - twitter: @LauT
   iex(1)> 5/2
   2.5
   iex(2)> 5/"Orlando"
   ** (ArithmeticError) bad
   argument in arithmetic
   expression
   :erlang./(5, "Orlando")
   

   View Slide

7. Lau Taarnskov - twitter: @LauT
   We want errors instead
   of non-sensical results
   

   View Slide

8. Lau Taarnskov - twitter: @LauT
   Explicit data
   

   View Slide

9. Lau Taarnskov - twitter: @LauT
   

   View Slide

10. Lau Taarnskov - twitter: @LauT
    Mars Climate Orbiter
    Mission cost: $327.6 million
    Mission failure
    after a 286 day journey to Mars
    

    View Slide

11. Lau Taarnskov - twitter: @LauT
    Newton-seconds? Oh,
    we used pound seconds.
    

    View Slide

12. Lau Taarnskov - twitter: @LauT
    5, 6, 3, 9, 4, 5…
    

    View Slide

13. Lau Taarnskov - twitter: @LauT
    {5, :lbs_s}, {6, :lbs_s},
    {3, :lbs_s}, {9, :lbs_s},
    {4, :lbs_s}, {5, :lbs_s}…
    

    View Slide

14. Lau Taarnskov - twitter: @LauT
    %ThrusterData{amount: 5, unit: :lbs_s},
    %ThrusterData{amount: 6, unit: :lbs_s},
    %ThrusterData{amount: 3, unit: :lbs_s},
    

    View Slide

15. Lau Taarnskov - twitter: @LauT
    def process_thruster_data(%{amount: amount, unit: :n_s}) do
    # ...
    end
    ** (FunctionClauseError) no function clause matching in
    ThrustProcessor.process_thruster_data/1
    thruster.ex:12:
    ThrustProcessor.process_thruster_data(%ThrusterData{amou
    nt: 3, unit: :lbs_s})
    thruster.ex:17: (file)
    (elixir) lib/code.ex:363: Code.require_file/2
    

    View Slide

16. Lau Taarnskov - twitter: @LauT
    Different units of time
    and date
    

    View Slide

17. Lau Taarnskov - twitter: @LauT
    2016
    2016 September
    2016 September 2nd
    2016 September 2nd at 14:01:03
    2016-09-02 at 14:01:03 in New York
    14:01
    14:01:03
    14:01:03.9472
    ….
    

    View Slide

18. Lau Taarnskov - twitter: @LauT
    One type to
    rule them all?
    

    View Slide

19. Lau Taarnskov - twitter: @LauT
    2016-09-02
    2016-09-02 00:00:00.000 UTC
    

    View Slide

20. Lau Taarnskov - twitter: @LauT
    06:10
    2001-01-01 06:10:00.000 UTC
    

    View Slide

21. Lau Taarnskov - twitter: @LauT
    2001-01-01 00:00:00.000
    2001-01-01 06:10:00.000 UTC
    

    View Slide

22. Lau Taarnskov - twitter: @LauT
    6:10
    What year is that in?
    2001
    (!!!!!!!)
    

    View Slide

23. Lau Taarnskov - twitter: @LauT
    2016-09-02
    At what hour and
    minute? 00:00
    (!!!)
    

    View Slide

24. Lau Taarnskov - twitter: @LauT
    Year
    Year with month
    Year, month, day of month
    Hour
    Hour and minute
    Hour and minute and second
    …
    

    View Slide

25. Lau Taarnskov - twitter: @LauT
    The structs in the
    Calendar library
    

    View Slide

26. Lau Taarnskov - twitter: @LauT
    Types in Calendar in 2014
    Calendar.Date
    Calendar.Time
    Calendar.NaiveDateTime
    Calendar.DateTime
    

    View Slide

27. Lau Taarnskov - twitter: @LauT
    Date: year, month, day
    

    View Slide

28. Lau Taarnskov - twitter: @LauT
    Time: hour, minute,
    second, microsecond
    

    View Slide

29. Lau Taarnskov - twitter: @LauT
    NaiveDateTime: year,
    month, day, hour, minute,
    second, microsecond
    

    View Slide

30. Lau Taarnskov - twitter: @LauT
    DateTime: year, month,
    day, hour, minute, second,
    microsecond, time zone,
    UTC offset, standard
    offset, zone abbreviation
    

    View Slide

31. Lau Taarnskov - twitter: @LauT
    Local vs Naive
    

    View Slide

32. Lau Taarnskov - twitter: @LauT
    JAVA 8
    Class LocalDate
    A date without a time-zone in the
    ISO-8601 calendar system, such
    as 2007-12-03.
    

    View Slide

33. Lau Taarnskov - twitter: @LauT
    local |ˈlōk(ə)l|
    
    adjective
    belonging or relating to a
    particular area or
    neighborhood, typically
    exclusively so: researching local
    history | the local post office.
    

    View Slide

34. Lau Taarnskov - twitter: @LauT
    

    View Slide

35. Lau Taarnskov - twitter: @LauT
    ~N[1970-01-01 00:00:00] |> DateTime.to_unix
    ** (FunctionClauseError) no function clause
    matching in DateTime.to_unix/2
    (elixir) lib/calendar.ex:1078:
    DateTime.to_unix(~N[1970-01-01
    00:00:00], :seconds)
    

    View Slide

36. Lau Taarnskov - twitter: @LauT
    The structs built into
    Elixir 1.3
    

    View Slide

37. Lau Taarnskov - twitter: @LauT
    Types in Calendar in 2014 Types in Elixir 1.3 in 2016
    Calendar.Date Date
    Calendar.Time Time
    Calendar.NaiveDateTime NaiveDateTime
    Calendar.DateTime DateTime
    

    View Slide

38. Lau Taarnskov - twitter: @LauT
    Sigils
    ~D[2016-09-02]
    ~T[14:15:00]
    ~N[2016-09-02 14:15:00]
    

    View Slide

39. Lau Taarnskov - twitter: @LauT
    %DateTime{calendar:
    Calendar.ISO, day: 1, hour:
    0, microsecond: {0, 0}, …
    

    View Slide

40. Lau Taarnskov - twitter: @LauT
    %DateTime{calendar:
    Calendar.ISO, day: 1, hour:
    0, microsecond: {0, 0}, …
    

    View Slide

41. Lau Taarnskov - twitter: @LauT
    "2016-09-02 14:15:00.1234” |>
    NaiveDateTime.from_iso8601!
    ~N[2016-09-02 14:15:00.1234]
    "2016-09-02 14:15:00.1” |>
    NaiveDateTime.from_iso8601!
    ~N[2016-09-02 14:15:00.1]
    Significant fractional seconds
    

    View Slide

42. Lau Taarnskov - twitter: @LauT
    "2016-09-02 14:15:00.1234” |>
    NaiveDateTime.from_iso8601! |> Map.get(:microsecond)
    {123400, 4}
    "2016-09-02 14:15:00.10” |>
    NaiveDateTime.from_iso8601! |> Map.get(:microsecond)
    {100000, 2}
    "2016-09-02 14:15:00” |> NaiveDateTime.from_iso8601!
    |> Map.get(:microsecond)
    {0, 0}
    Significant fractional seconds
    

    View Slide

43. Lau Taarnskov - twitter: @LauT
    Time zones and more
    functionality with the
    Calendar library
    

    View Slide

44. Lau Taarnskov - twitter: @LauT
    The Calendar library
    

    View Slide

45. Lau Taarnskov - twitter: @LauT
    ~N[1970-01-01 00:00:00]
    |> Calendar.NaiveDateTime.to_date_time_utc
    |> DateTime.to_unix
    0
    

    View Slide

46. Lau Taarnskov - twitter: @LauT
    DateTime.from_unix!(1472836167)
    %DateTime{calendar: Calendar.ISO, day: 2,
    hour: 17, microsecond: {0, 0}, minute: 9,
    month: 9, second: 27, std_offset: 0,
    time_zone: "Etc/UTC",
    utc_offset: 0, year: 2016, zone_abbr: "UTC"}
    

    View Slide

47. Lau Taarnskov - twitter: @LauT
    DateTime.from_unix!(1472836167)
    |> Calendar.DateTime.shift_zone!("America/New_York")
    %DateTime{calendar: Calendar.ISO, day: 2, hour: 13,
    microsecond: {0, 0}, minute: 9, month: 9, second: 27,
    std_offset: 3600,
    time_zone: "America/New_York", utc_offset: -18000,
    year: 2016, zone_abbr: "EDT"}
    

    View Slide

48. Lau Taarnskov - twitter: @LauT
    DateTime.from_unix!(1472836167)
    |> Calendar.DateTime.shift_zone(“America/New_York”)
    |> DateTime.to_iso8601
    "2016-09-02T13:09:27-04:00"
    

    View Slide

49. Lau Taarnskov - twitter: @LauT
    DateTime.from_unix(1472836167)
    |> Calendar.DateTime.shift_zone!(“America/New_York”)
    |> Calendar.Strftime.strftime!("%Y %B %d, %H:%M:%S %Z")
    "2016 September 02, 13:09:27 EDT"
    

    View Slide

50. Lau Taarnskov - twitter: @LauT
    ~D[2016-09-02]
    |> Calendar.Date.friday?
    true
    

    View Slide

51. Lau Taarnskov - twitter: @LauT
    ~D[2016-09-02]
    |> Calendar.Date.before?
    (~D[2016-09-03])
    true
    

    View Slide

52. Lau Taarnskov - twitter: @LauT
    ~D[2016-09-02]
    |>Calendar.Date.next_day!
    ~D[2016-09-03]
    

    View Slide

53. Lau Taarnskov - twitter: @LauT
    Calendar.Date.today(“Amer
    ica/New_York")
    |> Calendar.Date.next_day!
    ~D[2016-09-03]
    

    View Slide

54. Lau Taarnskov - twitter: @LauT
    ~D[2016-09-02]
    |> Calendar.Date.add!(7)
    |> Date.to_iso8601
    "2016-09-09"
    

    View Slide

55. Lau Taarnskov - twitter: @LauT
    Getting the time zone
    of a user
    

    View Slide

56. Lau Taarnskov - twitter: @LauT
    Persistence in Ecto
    

    View Slide

57. Lau Taarnskov - twitter: @LauT
    The Calecto library
    

    View Slide

58. Lau Taarnskov - twitter: @LauT
    You want to select a
    type that fits the data
    

    View Slide

59. Lau Taarnskov - twitter: @LauT
    Thank you
    

    View Slide

60. Lau Taarnskov - twitter: @LauT
    Questions
    

    View Slide