diff --git a/app/controllers/report_controller.rb b/app/controllers/report_controller.rb
--- a/app/controllers/report_controller.rb
+++ b/app/controllers/report_controller.rb
@@ -1,18 +1,70 @@
 class ReportController < ApplicationController
   def login_stat
     @logins = Array.new
-    login = Login.all
 
-    date_and_time = '%y-%m-%d %H:%M'
-    since_time = strptime(params[:since_datetime],date_and_time)
-    until_time = strptime(params[:until_datetime],date_and_time)
+    date_and_time = '%Y-%m-%d %H:%M'
+    begin
+      @since_time = DateTime.strptime(params[:since_datetime],date_and_time)
+    rescue
+      @since_time = DateTime.new(1000,1,1)
+    end
+    begin
+      @until_time = DateTime.strptime(params[:until_datetime],date_and_time)
+    rescue
+      @until_time = DateTime.new(3000,1,1)
+    end
     
     User.all.each do |user|
       @logins << { login: user.login, 
                    full_name: user.full_name, 
-                   count: Login.where(user_id: user.id).count(:id), 
-                   min: Login.where(user_id: user.id).maximum(:created_at),
-                   max: Login.where(user_id: user.id).minimum(:created_at) }
+                   count: Login.where("user_id = ? AND created_at >= ? AND created_at <= ?",
+                                      user.id,@since_time,@until_time)
+                          .count(:id),
+                   min: Login.where("user_id = ? AND created_at >= ? AND created_at <= ?",
+                                      user.id,@since_time,@until_time)
+                          .minimum(:created_at),
+                   max: Login.where("user_id = ? AND created_at >= ? AND created_at <= ?",
+                                      user.id,@since_time,@until_time)
+                          .maximum(:created_at)
+                 }
+    end
+  end
+
+  def submission_stat
+
+    date_and_time = '%Y-%m-%d %H:%M'
+    begin
+      @since_time = DateTime.strptime(params[:since_datetime],date_and_time)
+    rescue
+      @since_time = DateTime.new(1000,1,1)
+    end
+    begin
+      @until_time = DateTime.strptime(params[:until_datetime],date_and_time)
+    rescue
+      @until_time = DateTime.new(3000,1,1)
+    end
+
+    @submissions = {}
+
+    User.find_each do |user|
+      @submissions[user.id] = { login: user.login, full_name: user.full_name, count: 0, sub: { } }
+    end
+
+    Submission.where("submitted_at >= ? AND submitted_at <= ?",@since_time,@until_time).find_each do |s|
+      if not @submissions[s.user_id][:sub].has_key?(s.problem_id)
+        a = nil
+        begin
+          a = Problem.find(s.problem_id)
+        rescue
+          a = nil
+        end
+        @submissions[s.user_id][:sub][s.problem_id] = 
+          { prob_name: (a ? a.full_name : '(NULL)'),
+            sub_ids: [s.id] } 
+      else
+        @submissions[s.user_id][:sub][s.problem_id][:sub_ids] << s.id
+      end
+      @submissions[s.user_id][:count] += 1
     end
   end
 end