Issues CSV uses Excel compatible dates

app/views/projects/issues/index.csv.ruby

@@ -6,9 +6,9 @@ columns = {
   'Author' => 'author_name',
   'Assignee' => 'assignee_name',
   'Confidential' => 'confidential',
-  'Due Date' => 'due_date',
-  'Created At' => 'created_at',
-  'Updated At' => 'updated_at',
+  'Due Date' => -> (issue) { issue.due_date&.strftime('%Y-%m-%d') },
+  'Created At (UTC)' => -> (issue) { issue.created_at&.strftime('%Y-%m-%d %H:%M:%S') },
+  'Updated At (UTC)' => -> (issue) { issue.updated_at&.strftime('%Y-%m-%d %H:%M:%S') },
   'Milestone' => -> (issue) { issue.milestone&.title },
   'Labels' => -> (issue) { issue.label_names.join(',').presence },
 }

spec/features/issues/csv_spec.rb

@@ -29,7 +29,14 @@ describe 'Issues csv', feature: true do
     let(:milestone) { create(:milestone, title: "v1.0", project: project) }
 
     before do
-      issue.update!(milestone: milestone, assignee: user, description: 'Issue with details', labels: [label1, label2])
+      issue.update!(milestone: milestone,
+                    assignee: user,
+                    description: 'Issue with details',
+                    due_date: DateTime.new(2014, 3, 2),
+                    created_at: DateTime.new(2015, 4, 3, 2, 1, 0),
+                    updated_at: DateTime.new(2016, 5, 4, 3, 2, 1),
+                    labels: [label1, label2])
+
       visit namespace_project_issues_path(project.namespace, project, format: :csv)
     end
 
@@ -60,6 +67,19 @@ describe 'Issues csv', feature: true do
     specify 'labels' do
       expect(csv[0]['Labels']).to eq 'Feature,labels'
     end
+
+    specify 'due_date' do
+      expect(csv[0]['Due Date']).to eq '2014-03-02'
+    end
+
+
+    specify 'created_at' do
+      expect(csv[0]['Created At (UTC)']).to eq '2015-04-03 02:01:00'
+    end
+
+    specify 'updated_at' do
+      expect(csv[0]['Updated At (UTC)']).to eq '2016-05-04 03:02:01'
+    end
   end
 
   context 'with minimal details' do