diff --git a/app/controllers/time_accountings_controller.rb b/app/controllers/time_accountings_controller.rb
index 2d0102f52..0860b0edd 100644
--- a/app/controllers/time_accountings_controller.rb
+++ b/app/controllers/time_accountings_controller.rb
@@ -466,8 +466,9 @@ class TimeAccountingsController < ApplicationController
 
     if timezone.present?
       offset = time.in_time_zone(timezone).utc_offset
-      time -= offset
+      time += offset
     end
-    time.utc.iso8601.to_s.sub(/Z$/, '')
+    local_time = time.utc.iso8601.to_s.sub(/Z$/, '')
+    local_time.sub(/T/, ' ')
   end
 end
diff --git a/spec/requests/time_accounting_spec.rb b/spec/requests/time_accounting_spec.rb
index 74cde3809..87d69297a 100644
--- a/spec/requests/time_accounting_spec.rb
+++ b/spec/requests/time_accounting_spec.rb
@@ -61,5 +61,9 @@ RSpec.describe 'Time Accounting API endpoints', type: :request do
         expect(response['Content-Type']).to eq('application/vnd.ms-excel')
       end
     end
+
+    it 'does convert UTC timestamp to local system based timestamp' do
+      expect(TimeAccountingsController.new.instance_eval { time_in_localtime_for_excel(Time.parse('2019-08-08T01:00:05Z').in_time_zone, 'Europe/Berlin') }).to eq('2019-08-08 03:00:05')
+    end
   end
 end