extract dates constants to book class and freeze them

Author: kamilhism

lib/creek/book.rb

@@ -1,5 +1,6 @@
 require 'zip/filesystem'
 require 'nokogiri'
+require 'date'
 
 module Creek
 
@@ -9,6 +10,9 @@ class Creek::Book
                 :sheets,
                 :shared_strings
 
+    DATE_1900 = Date.new(1899, 12, 30).freeze
+    DATE_1904 = Date.new(1904, 1, 1).freeze
+
     def initialize path, options = {}
       check_file_extension = options.fetch(:check_file_extension, true)
       if check_file_extension
@@ -44,13 +48,13 @@ def base_date
         # Default to 1900 (minus one day due to excel quirk) but use 1904 if
         # it's set in the Workbook's workbookPr
         # http://msdn.microsoft.com/en-us/library/ff530155(v=office.12).aspx
-        result = Date.new(1899, 12, 30) # default
+        result = DATE_1900 # default
 
         doc = @files.file.open "xl/workbook.xml"
         xml = Nokogiri::XML::Document.parse doc
         xml.css('workbookPr[date1904]').each do |workbookPr|
           if workbookPr['date1904'] =~ /true|1/i
-            result = Date.new(1904, 1, 1)
+            result = DATE_1904
             break
           end
         end

lib/creek/styles/constants.rb

@@ -1,5 +1,3 @@
-require 'date'
-
 module Creek
   class Styles
     module Constants
@@ -38,9 +36,6 @@ module Constants
         48 => :bignum,         # ##0.0E+0
         49 => :unsupported     # @
       }
-
-      DATE_SYSTEM_1900 = Date.new(1899, 12, 30)
-      DATE_SYSTEM_1904 = Date.new(1904, 1, 1)
     end
   end
 end

lib/creek/styles/converter.rb

@@ -81,7 +81,7 @@ def self.convert_date(value, options)
         fraction_of_24               = value - days_since_date_system_start
 
         # http://stackoverflow.com/questions/10559767/how-to-convert-ms-excel-date-from-float-to-date-format-in-ruby
-        date = options.fetch(:base_date, DATE_SYSTEM_1900) + days_since_date_system_start
+        date = options.fetch(:base_date, Date.new(1899, 12, 30)) + days_since_date_system_start
 
         if fraction_of_24 > 0 # there is a time associated
           seconds = (fraction_of_24 * 86400).round