--- a/plugins/redmine_workload/lib/redmine_workload/wl_date_tools.rb
+++ b/plugins/redmine_workload/lib/redmine_workload/wl_date_tools.rb
@@ -76,7 +76,7 @@ class WlDateTools
   end
 
   def self.holiday?(day)
-    !WlNationalHoliday.where('start <= ? AND end >= ?', day, day).empty?
+    !WlNationalHoliday.where(start: ..day).where(end: day..).empty?
   end
 
   def self.vacation?(day, assignee)
