Rapide correction, mysql ne comprend que la fonction extract pour extraire mois et année

app/controllers/regions_controller.rb

@@ -4,9 +4,12 @@ class RegionsController < InheritedResources::Base
 
     @city_events = Event.group(:city).having('count(city) > 3').order('count(city) desc').count(:city)
 
+    # Used in sqlite
+    #.group('strftime("%Y", start_time)')
+    #.group('strftime("%m", start_time)')
     @month_events = Event
-      .group('strftime("%Y", start_time)')
-      .group('strftime("%m", start_time)')
+      .group('extract(year from start_time)')
+      .group('extract(month from start_time)')
       .count()
   end
 end