diff --git a/CHANGELOG b/CHANGELOG
index 44ea3d6e01d..43b3b33155d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -30,6 +30,7 @@ v 8.12.0 (unreleased)
   - Fix file permissions change when updating a file on the Gitlab UI !5979
   - Change merge_error column from string to text type
   - Reduce contributions calendar data payload (ClemMakesApps)
+  - Replace contributions calendar timezone payload with dates (ClemMakesApps)
   - Add `web_url` field to issue, merge request, and snippet API objects (Ben Boeckel)
   - Enable pipeline events by default !6278
   - Move parsing of sidekiq ps into helper !6245 (pascalbetz)
diff --git a/app/assets/javascripts/users/calendar.js b/app/assets/javascripts/users/calendar.js
index b8da7c4f297..3bd4c3c066f 100644
--- a/app/assets/javascripts/users/calendar.js
+++ b/app/assets/javascripts/users/calendar.js
@@ -29,7 +29,7 @@
         date.setDate(date.getDate() + i);
 
         var day = date.getDay();
-        var count = timestamps[date.getTime() * 0.001];
+        var count = timestamps[dateFormat(date, 'yyyy-mm-dd')];
 
         // Create a new group array if this is the first day of the week
         // or if is first object
diff --git a/app/controllers/users_controller.rb b/app/controllers/users_controller.rb
index a99632454d9..a4bedb3bfe6 100644
--- a/app/controllers/users_controller.rb
+++ b/app/controllers/users_controller.rb
@@ -73,7 +73,7 @@ class UsersController < ApplicationController
 
   def calendar
     calendar = contributions_calendar
-    @timestamps = calendar.timestamps
+    @activity_dates = calendar.activity_dates
 
     render 'calendar', layout: false
   end
diff --git a/app/views/users/calendar.html.haml b/app/views/users/calendar.html.haml
index 77f2ddefb1e..09ff8a76d27 100644
--- a/app/views/users/calendar.html.haml
+++ b/app/views/users/calendar.html.haml
@@ -4,6 +4,6 @@
     Summary of issues, merge requests, and push events
 :javascript
   new Calendar(
-    #{@timestamps.to_json},
+    #{@activity_dates.to_json},
     '#{user_calendar_activities_path}'
-  );
+  );
\ No newline at end of file
diff --git a/lib/gitlab/contributions_calendar.rb b/lib/gitlab/contributions_calendar.rb
index bd681f03173..b164f5a2eea 100644
--- a/lib/gitlab/contributions_calendar.rb
+++ b/lib/gitlab/contributions_calendar.rb
@@ -1,16 +1,16 @@
 module Gitlab
   class ContributionsCalendar
-    attr_reader :timestamps, :projects, :user
+    attr_reader :activity_dates, :projects, :user
 
     def initialize(projects, user)
       @projects = projects
       @user = user
     end
 
-    def timestamps
-      return @timestamps if @timestamps.present?
+    def activity_dates
+      return @activity_dates if @activity_dates.present?
 
-      @timestamps = {}
+      @activity_dates = {}
       date_from = 1.year.ago
 
       events = Event.reorder(nil).contributions.where(author_id: user.id).
@@ -19,18 +19,17 @@ module Gitlab
         select('date(created_at) as date, count(id) as total_amount').
         map(&:attributes)
 
-      dates = (1.year.ago.to_date..Date.today).to_a
+      activity_dates = (1.year.ago.to_date..Date.today).to_a
 
-      dates.each do |date|
-        date_id = date.to_time.to_i.to_s
+      activity_dates.each do |date|
         day_events = events.find { |day_events| day_events["date"] == date }
 
         if day_events
-          @timestamps[date_id] = day_events["total_amount"]
+          @activity_dates[date] = day_events["total_amount"]
         end
       end
 
-      @timestamps
+      @activity_dates
     end
 
     def events_by_date(date)
diff --git a/spec/features/calendar_spec.rb b/spec/features/calendar_spec.rb
new file mode 100644
index 00000000000..fd5fbaf2af4
--- /dev/null
+++ b/spec/features/calendar_spec.rb
@@ -0,0 +1,39 @@
+require 'spec_helper'
+
+feature 'Contributions Calendar', js: true, feature: true do
+  include WaitForAjax
+
+  let(:contributed_project) { create(:project, :public) }
+
+  before do
+    login_as :user
+
+    issue_params = { title: 'Bug in old browser' }
+    Issues::CreateService.new(contributed_project, @user, issue_params).execute
+
+    # Push code contribution
+    push_params = {
+      project: contributed_project,
+      action: Event::PUSHED,
+      author_id: @user.id,
+      data: { commit_count: 3 }
+    }
+
+    Event.create(push_params)
+
+    visit @user.username
+    wait_for_ajax
+  end
+
+  it 'displays calendar', js: true do
+    expect(page).to have_css('.js-contrib-calendar')
+  end
+
+  it 'displays calendar activity log', js: true do
+    expect(find('.content_list .event-note')).to have_content "Bug in old browser"
+  end
+
+  it 'displays calendar activity square color', js: true do
+    expect(page).to have_selector('.user-contrib-cell[fill=\'#acd5f2\']', count: 1)
+  end
+end