eqon133
Ecto, Phoenix and utc datetime
Hello,
I have a Phoenix app using Html.Form datetime_select
I fill user input using Timex zone convert in Europe/Tallinn (UTC+2):
Saved result is same as input
Shouldn’t it be saved as UTC, since all times are UTC in db?
field(:planned_start_at, :utc_datetime)
Q: Where should this convert to UTC? Should i create custom Ecto.Type for this? or in changeset before insert? or can Ecto handle it itself?
inserted_at and updated_at are correctly in UTC
Phoenix 1.4, Ecto 3.0, Postgres
Thanks,
Marked As Solved
eqon133
I will provide my solution here. So i created custom Ecto.Type which will receive local datetime and timezone. And that will convert it to utc.
@behaviour Ecto.Type
def type(), do: :utc_datetime
..
def cast(%{"datetimelocal" => datetimelocal, "tz" => tz}) do
case Timex.parse(datetimelocal, "{ISO:Extended}") do
{:error, _error} ->
Ecto.Type.cast(type(), nil)
{:ok, value} ->
Ecto.Type.cast(type(), Timex.to_datetime(value, tz))
end
end
..
def cast(data), do: Ecto.Type.cast(type(), data)
Also Liked
wojtekmach
When casting a non-UTC %DateTime{} to :utc_datetime it’s gonna be converted to UTC timezone as we can do this safely. After casting it’s all UTC.
As far as storing future date times in UTC that’s indeed dangerous. See @Lau’s excellent blog posts: http://www.creativedeletion.com
OvermindDL1
As I recall :utc_datetime stores timezone information where :naive_datetime does not and stores things as utc always. I think… ^.^;
Regardless, datetimes in the future you want to store with timezone information. Timezones change all the time and if someone plans something on, say, March 18th at 5pm, and daylight savings starts on March 20th but then that gets changed to start on March 12th then if you stored the datetime as utc in the database then you are off by an hour where if you stored it with the proper timezone then it will still be correct. 
Past times are of course fine to store timezoneless.
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