convert date range filter to client's timezone before filtering orders

app/views/admin/reports/_date_range_form.html.haml

@@ -8,3 +8,7 @@
     %span.range-divider
       %i.icon-arrow-right
     = f.text_field "#{field}_lt", :class => 'datetimepicker datepicker-to', :placeholder => t(:stop), data: { controller: "flatpickr", "flatpickr-enable-time-value": true, "flatpickr-default-date-value": "endOfDay" }
+= hidden_field_tag "time_zone"
+:javascript
+  document.querySelector("input[name='time_zone']").value = Intl.DateTimeFormat().resolvedOptions().timeZone
+

lib/reporting/reports/customers/base.rb

@@ -55,6 +55,10 @@ def filter_to_completed_at(orders)
 
           return orders if min.blank? || max.blank?
 
+          if client_time_zone.present?
+            min = convert_to_client_time_zone(min)
+            max = convert_to_client_time_zone(max)
+          end
           orders.where(completed_at: [min..max])
         end
 
@@ -81,6 +85,18 @@ def last_completed_order(orders)
         def last_completed_order_date(orders)
           last_completed_order(orders).completed_at&.to_date
         end
+
+        def convert_to_client_time_zone(datetime)
+          DateTime.parse(datetime).change(offset: utc_offset)
+        end
+
+        def client_time_zone
+          ActiveSupport::TimeZone[params["time_zone"] || ""]
+        end
+
+        def utc_offset
+          ActiveSupport::TimeZone[client_time_zone].formatted_offset
+        end
       end
     end
   end