Merge pull request #5612 from ashmaroli/win-tz

Merge pull request 5612

Gemfile

@@ -79,6 +79,9 @@ group :jekyll_optional_dependencies do
     gem "classifier-reborn", "~> 2.0"
     gem "liquid-c", "~> 3.0"
   end
+
+  # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
+  gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
 end
 
 #

docs/_docs/windows.md

@@ -34,6 +34,19 @@ the site generation process. It can be done with the following command:
 $ chcp 65001
 ```
 
+## Timezone Management
+
+Since Windows doesn't have a native source of zoneinfo data, the Ruby Interpreter would not understand IANA Timezones and hence using them had the `TZ` environment variable default to UTC/GMT 00:00.  
+Though Windows users could alternatively define their blog's timezone by setting the key to use POSIX format of defining timezones, it wasn't as user-friendly when it came to having the clock altered to changing DST-rules.
+
+Jekyll now uses a rubygem to internally configure Timezone based on established [IANA Timezone Database](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones).  
+While 'new' blogs created with Jekyll v3.4 and greater, will have the following added to their 'Gemfile' by default, existing sites *will* have to update their 'Gemfile' (and installed) to enable development on Windows:
+
+```ruby
+# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
+gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
+```
+
 ## Auto-regeneration
 
 As of v1.3.0, Jekyll uses the `listen` gem to watch for changes when the

features/site_configuration.feature

@@ -162,7 +162,7 @@ Feature: Site configuration
       And I have an "index.html" page with layout "page" that contains "site index page"
       And I have a configuration file with:
         | key         | value            |
-        | timezone    | UTC+04:00    |
+        | timezone    | America/New_York |
       And I have a _posts directory
       And I have the following posts:
         | title     | date                   | layout  | content             |
@@ -172,8 +172,10 @@ Feature: Site configuration
       Then I should get a zero exit status
     And the _site directory should exist
       And I should see "Page Layout: 2" in "_site/index.html"
-      And I should see "Post Layout: <p>content for entry1.</p>\n built at 2013-04-09T23:22:00-04:00" in "_site/2013/04/09/entry1.html"
-      And I should see "Post Layout: <p>content for entry2.</p>\n built at 2013-04-10T03:14:00-04:00" in "_site/2013/04/10/entry2.html"
+      And I should see "Post Layout: <p>content for entry1.</p>\n built at 2013-04-09T23:22:00-04:00" in "_site/2013/04/09/entry1.html" unless Windows
+      And I should see "Post Layout: <p>content for entry1.</p>\n built at 2013-04-09T22:22:00-05:00" in "_site/2013/04/09/entry1.html" if on Windows
+      And I should see "Post Layout: <p>content for entry2.</p>\n built at 2013-04-10T03:14:00-04:00" in "_site/2013/04/10/entry2.html" unless Windows
+      And I should see "Post Layout: <p>content for entry2.</p>\n built at 2013-04-10T02:14:00-05:00" in "_site/2013/04/10/entry2.html" if on Windows
 
     Scenario: Generate proper dates with explicitly set timezone (different than posts' time)
       Given I have a _layouts directory
@@ -182,7 +184,7 @@ Feature: Site configuration
       And I have an "index.html" page with layout "page" that contains "site index page"
       And I have a configuration file with:
         | key         | value                |
-        | timezone    | UTC+10:00    |
+        | timezone    | Pacific/Honolulu     |
       And I have a _posts directory
       And I have the following posts:
         | title     | date                   | layout  | content             |

lib/jekyll.rb

@@ -119,7 +119,11 @@ module Jekyll
     # Returns nothing
     # rubocop:disable Style/AccessorMethodName
     def set_timezone(timezone)
-      ENV["TZ"] = timezone
+      ENV["TZ"] = if Utils::Platforms.really_windows?
+                    Utils::WinTZ.calculate(timezone)
+                  else
+                    timezone
+                  end
     end
     # rubocop:enable Style/AccessorMethodName
 

lib/jekyll/commands/new.rb

@@ -84,6 +84,10 @@ gem "minima", "~> 2.0"
 group :jekyll_plugins do
    gem "jekyll-feed", "~> 0.6"
 end
+
+# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
+gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
+
 RUBY
         end
 

lib/jekyll/utils.rb

@@ -4,6 +4,7 @@ module Jekyll
     extend self
     autoload :Platforms, "jekyll/utils/platforms"
     autoload :Ansi, "jekyll/utils/ansi"
+    autoload :WinTZ, "jekyll/utils/win_tz"
 
     # Constants for use in #slugify
     SLUGIFY_MODES = %w(raw default pretty ascii).freeze

lib/jekyll/utils/win_tz.rb

@@ -0,0 +1,73 @@
+module Jekyll
+  module Utils
+    module WinTZ
+      extend self
+
+      # Public: Calculate the Timezone for Windows when the config file has a defined
+      #         'timezone' key.
+      #
+      # timezone - the IANA Time Zone specified in "_config.yml"
+      #
+      # Returns a string that ultimately re-defines ENV["TZ"] in Windows
+      def calculate(timezone)
+        External.require_with_graceful_fail("tzinfo")
+        tz = TZInfo::Timezone.get(timezone)
+        difference = Time.now.to_i - tz.now.to_i
+        #
+        # POSIX style definition reverses the offset sign.
+        #   e.g. Eastern Standard Time (EST) that is 5Hrs. to the 'west' of Prime Meridian
+        #   is denoted as:
+        #     EST+5 (or) EST+05:00
+        # Reference: http://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
+        sign = difference < 0 ? "-" : "+"
+        offset = sign == "-" ? "+" : "-" unless difference.zero?
+        #
+        # convert the difference (in seconds) to hours, as a rational number, and perform
+        # a modulo operation on it.
+        modulo = modulo_of(rational_hour(difference))
+        #
+        # Format the hour as a two-digit number.
+        # Establish the minutes based on modulo expression.
+        hh = format("%02d", absolute_hour(difference).ceil)
+        mm = modulo.zero? ? "00" : "30"
+
+        Jekyll.logger.debug "Timezone:", "#{timezone} #{offset}#{hh}:#{mm}"
+        #
+        # Note: The 3-letter-word below doesn't have a particular significance.
+        "WTZ#{sign}#{hh}:#{mm}"
+      end
+
+      private
+
+      # Private: Convert given seconds to an hour as a rational number.
+      #
+      # seconds - supplied as an integer, it is converted to a rational number.
+      # 3600 - no. of seconds in an hour.
+      #
+      # Returns a rational number.
+      def rational_hour(seconds)
+        seconds.to_r/3600
+      end
+
+      # Private: Convert given seconds to an hour as an absolute number.
+      #
+      # seconds - supplied as an integer, it is converted to its absolute.
+      # 3600 - no. of seconds in an hour.
+      #
+      # Returns an integer.
+      def absolute_hour(seconds)
+        seconds.abs/3600
+      end
+
+      # Private: Perform a modulo operation on a given fraction.
+      #
+      # fraction - supplied as a rational number, its numerator is divided
+      #            by its denominator and the remainder returned.
+      #
+      # Returns an integer.
+      def modulo_of(fraction)
+        fraction.numerator % fraction.denominator
+      end
+    end
+  end
+end