Remove Timex dependency

[matthewlehner]

Creating this issue to track where Timex is used currently and to track removing it.

To make these PRs a bit easier to review, I will start opening one for each Timex function call.

Timex API Usage Inventory

The following Timex functions are used across the codebase and need stdlib replacements:

Source files

• use Timex — lib/ical/serialize.ex:3 → Remove
• Timex.format/2 — lib/ical/serialize.ex:26,37,48 → Calendar.strftime/3
• Timex.to_datetime/1 — lib/ical/serialize.ex:63 → NaiveDateTime.from_erl!/1 + DateTime.from_naive!/2
• Timex.Timezone.Utils.to_olson/1 — lib/ical/deserialize.ex:424 → looks like there's work on this already started!
• Timex.parse/2 — lib/ical/deserialize.ex:466,484,491 → Binary pattern matching
• Timex.compare/2 — lib/ical/recurrence.ex:207 → DateTime.compare/2 / Date.compare/2
• Timex.shift/2 — lib/ical/recurrence.ex:281 → DateTime.shift/2 / Date.shift/2
• Timex.AmbiguousDateTime — lib/ical/recurrence.ex:282 → Remove
• Timex.weekday/1 — lib/ical/recurrence.ex:326 → Date.day_of_week/1

Test and support files

• Timex.to_datetime({{y,m,d},{h,m,s}}) — fixtures.ex, event_test.exs, ical_test.exs, deserialize_test.exs → ~U[...] sigils
• Timex.to_date({y,m,d}) — event_test.exs → ~D[...] sigils
• Timex.to_datetime/2 (with timezone) — event_test.exs → DateTime.shift_zone!/3
• Timex.Timezone.convert/2 — ical_test.exs, value_test.exs, deserialize_test.exs → DateTime.shift_zone!/3

Doc examples

• Timex.to_erl/1 — lib/ical/deserialize.ex:435,441,453
• Timex.to_date/1 — lib/ical/recurrence.ex:103,104

Deps

• Remove {:timex, "~> 3.4"} from mix.exs
• Remove Timex and transitive deps from mix.lock (mix deps.unlock --unused)
• Handle Calendar.TimeZoneDatabase config

[aseigo]

Really excellent survey, and we're already down three items!

[matthewlehner]

Just put up #35 to add timezone database config to the installation instructions.

There's some benchmarks and accuracy tests in this repo. I think based on the info here, it'd be worth recommending tz as the timezone database.

The two bits of info from that repo that seem relevant:

At the time of writing this,

• the output of Java, tz and time_zone_info is identical;
• tzdata generates a lot of wrong dates;
• zoneinfo generates wrong dates for some special time zones and for dates in the year 2038.

and

Time spent generating the result is logged in the console, giving some idea of the difference in terms of performance.

The time taken for each library to generate the output on my system are:

• ~50 seconds for tz
• ~50 seconds for time_zone_info
• ~80 seconds for zoneinfo
• ~160 seconds for tzdata

[aseigo]

#39 takes care of the last use of Timex in the list for the library source code :) We are nearly there!

[aseigo]

WRAPPED! :) Great work everyone...