ActiveSupport::TimeWithZone#dst? always returns true

[drssdinblck]

Steps to reproduce

Run rails c for a standard rails application.

Execute

Time.find_zone!('Berlin').parse('2020-01-01').dst?

Expected behavior

dst? should return false for January as this is not within daylight saving time.

Actual behavior

[29] pry(main)> Time.find_zone!('Berlin').parse('2020-01-01').dst?
=> true

System configuration

Rails version: 6.0.3.4

Ruby version: 2.7.2

OS: alpine3.12

The application is running in docker. This is the Dockerfile:

FROM ruby:2.7.2-alpine3.12
RUN apk add --no-cache --update build-base linux-headers git postgresql-dev tzdata less
WORKDIR /my-app
COPY Gemfile* ./
RUN bundle install
COPY . .

[composerinteralia]

I am not able to reproduce this locally (Ruby 2.7.2 with Rails 6.0.3.4). This returned false for me in the Rails console, and this reproduction script is passing:

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "rails", "6.0.3.4"
end

require "active_support"
require "active_support/core_ext/time/zones"
require "minitest/autorun"

class BugTest < Minitest::Test
  def test_stuff
    refute Time.find_zone!("Berlin").parse('2020-01-01').dst?
  end
end

[jonathanhefner]

@drssdinblck It sounds like you may be experiencing tzinfo/tzinfo#120 (see also #40427). Can you upgrade your tzinfo gem, and see if that resolves the problem?