How to convert timestamp to DateTime in Elixir?

Question

How to convert the time in milliseconds to Ecto.DateTime?

The time in milliseconds is the number of milliseconds elapsed since 1 January 1970 00:00:00 UTC.

Answer 1

Here's one way to do this while preserving the millisecond accuracy:

defmodule A do
  def timestamp_to_datetime(timestamp) do
    epoch = :calendar.datetime_to_gregorian_seconds({{1970, 1, 1}, {0, 0, 0}})
    datetime = :calendar.gregorian_seconds_to_datetime(epoch + div(timestamp, 1000))
    usec = rem(timestamp, 1000) * 1000
    %{Ecto.DateTime.from_erl(datetime) | usec: usec}
  end
end

Demo:

IO.inspect A.timestamp_to_datetime(1466329342388)

Output:

#Ecto.DateTime<2016-06-19 09:42:22.388000>