diff --git a/app/views/gantts/show.html.erb b/app/views/gantts/show.html.erb
index 7323e84ee..5b9aaa289 100644
--- a/app/views/gantts/show.html.erb
+++ b/app/views/gantts/show.html.erb
@@ -146,7 +146,7 @@ if show_days
   width =  zoom - 1
   %>
   <div style="left:<%= left %>px;top:37px;width:<%= width %>px;height:<%= height %>px;font-size:0.7em;<%= "background:#f1f1f1;" if wday > 5 %>" class="gantt_hdr">
-  <%= day_name(wday).first %>
+  <%= day_letter(wday) %>
   </div>
   <%
   left = left + width + 1
diff --git a/lib/redmine/i18n.rb b/lib/redmine/i18n.rb
index fade9a9ae..12445b450 100644
--- a/lib/redmine/i18n.rb
+++ b/lib/redmine/i18n.rb
@@ -58,6 +58,10 @@ module Redmine
       ::I18n.t('date.day_names')[day % 7]
     end
 
+    def day_letter(day)
+      ::I18n.t('date.abbr_day_names')[day % 7].first
+    end
+
     def month_name(month)
       ::I18n.t('date.month_names')[month]
     end
diff --git a/test/unit/lib/redmine/i18n_test.rb b/test/unit/lib/redmine/i18n_test.rb
index 2ec6dc2f9..d234ddf3c 100644
--- a/test/unit/lib/redmine/i18n_test.rb
+++ b/test/unit/lib/redmine/i18n_test.rb
@@ -25,6 +25,10 @@ class Redmine::I18nTest < ActiveSupport::TestCase
     User.current.language = nil
   end
 
+  def teardown
+    set_language_if_valid 'en'
+  end
+
   def test_date_format_default
     set_language_if_valid 'en'
     today = Date.today
@@ -155,6 +159,18 @@ class Redmine::I18nTest < ActiveSupport::TestCase
     end
   end
 
+  def test_day_name
+    set_language_if_valid 'fr'
+    assert_equal 'dimanche', day_name(0)
+    assert_equal 'jeudi', day_name(4)
+  end
+
+  def test_day_letter
+    set_language_if_valid 'fr'
+    assert_equal 'd', day_letter(0)
+    assert_equal 'j', day_letter(4)
+  end
+
   def test_valid_languages
     assert valid_languages.is_a?(Array)
     assert valid_languages.first.is_a?(Symbol)