Elixirschool: Add Date / Time lesson

[brain-geek]

Hey!

I've noticed that we actually don't have anything related to Date/Time stuff, which is present in Elixir now.

Do we actually have this content?

[ybur-yug]

Dates are briefly spoken about in sigils @brain-geek

from current master:

➜  elixir-school git:(master) ✗ grep -r --before-context=5 --after-context=5 Date lessons
lessons/basics/sigils.md-  - `~r` Generates a regular expression **with** escaping and interpolation
lessons/basics/sigils.md-  - `~S` Generates a string **with no** escaping or interpolation
lessons/basics/sigils.md-  - `~s` Generates a string **with** escaping and interpolation
lessons/basics/sigils.md-  - `~W` Generates a word list **with no** escaping or interpolation
lessons/basics/sigils.md-  - `~w` Generates a word list **with** escaping and interpolation
lessons/basics/sigils.md:  - `~N` Generates a `NaiveDateTime` struct
lessons/basics/sigils.md-
lessons/basics/sigils.md-A list of delimiters include:
lessons/basics/sigils.md-
lessons/basics/sigils.md-  - `<...>` A pair of pointy brackets
lessons/basics/sigils.md-  - `{...}` A pair of curly brackets
--
--
lessons/basics/sigils.md-
lessons/basics/sigils.md-iex> ~W/i love #{'e'}lixir school/
lessons/basics/sigils.md-["i", "love", "\#{'e'}lixir", "school"]
lessons/basics/sigils.md-```
lessons/basics/sigils.md-
lessons/basics/sigils.md:### NaiveDateTime
lessons/basics/sigils.md-
--
lessons/basics/sigils.md-
lessons/basics/sigils.md:A [NaiveDateTime](http://elixir-lang.org/docs/stable/elixir/NaiveDateTime.html) can be useful for quickly creating a struct to represent a `DateTime` **without** a timezone.
lessons/basics/sigils.md-
--
lessons/basics/sigils.md-
lessons/basics/sigils.md:For the most part, we should avoid creating a `NaiveDateTime` struct directly. However, it is very useful for pattern matching. For example:
lessons/basics/sigils.md-
lessons/basics/sigils.md-```elixir
--
lessons/basics/sigils.md-
lessons/basics/sigils.md-```elixir
lessons/basics/sigils.md:iex> NaiveDateTime.from_iso8601("2015-01-23 23:50:07") == {:ok, ~N[2015-01-23 23:50:07]}
lessons/basics/sigils.md-```
lessons/basics/sigils.md-
lessons/basics/sigils.md-## Creating Sigils
lessons/basics/sigils.md-
lessons/basics/sigils.md-One of the goals of Elixir is to be an extendable programming language. It should come as no surprise then that you can easily create your own custom sigils. In this example, we will create a sigil to convert a string to uppercase. As there is already a function for this in the Elixir Core (`String.upcase/1`), we will wrap our sigil around that function.

[doomspork]

@brain-geek / @ybur-yug2 / @nscyclone — I think there could be some value to a lesson under Basics covering Date and Time. Would one of you like to take a stab at it? If not, I'll have a go.

[brain-geek]

@doomspork Yeah, I can work on it. Though I expect first version to be quite short. 😄

[SophieDeBenedetto]

closing b/c addressed by https://github.com/elixirschool/elixirschool/pull/1571