diff --git app/models/time_entry.rb app/models/time_entry.rb
index 431c1a5..78c0b86 100644
--- app/models/time_entry.rb
+++ app/models/time_entry.rb
@@ -113,7 +113,7 @@ class TimeEntry < ActiveRecord::Base
   end
 
   def validate_time_entry
-    errors.add :hours, :invalid if hours && (hours < 0 || hours >= 1000)
+    errors.add :hours, :invalid if hours && (hours < 0 || hours > 24) || hours == 0
     errors.add :project_id, :invalid if project.nil?
     errors.add :issue_id, :invalid if (issue_id && !issue) || (issue && project!=issue.project) || @invalid_issue_id
     errors.add :activity_id, :inclusion if activity_id_changed? && project && !project.activities.include?(activity)
diff --git test/unit/time_entry_test.rb test/unit/time_entry_test.rb
index b86b1c5..7cc518d 100644
--- test/unit/time_entry_test.rb
+++ test/unit/time_entry_test.rb
@@ -133,6 +133,23 @@ class TimeEntryTest < ActiveSupport::TestCase
                          :description => 'IssueTest#test_create', :estimated_hours => '1:30')
     assert issue.save
     activity = TimeEntryActivity.find_by_name('Design')
+    
+    te = TimeEntry.create(:spent_on => '2010-01-01',
+                          :hours    => 1,
+                          :issue    => issue,
+                          :project  => project,
+                          :user     => anon,
+                          :activity => activity)
+    assert_equal 0, te.errors.count
+
+    te = TimeEntry.create(:spent_on => '2010-01-01',
+                          :hours    => 24,
+                          :issue    => issue,
+                          :project  => project,
+                          :user     => anon,
+                          :activity => activity)
+    assert_equal 0, te.errors.count
+    
     te = TimeEntry.create(:spent_on => '2010-01-01',
                           :hours    => 100000,
                           :issue    => issue,
@@ -140,6 +157,22 @@ class TimeEntryTest < ActiveSupport::TestCase
                           :user     => anon,
                           :activity => activity)
     assert_equal 1, te.errors.count
+
+    te = TimeEntry.create(:spent_on => '2010-01-01',
+                          :hours    => 0,
+                          :issue    => issue,
+                          :project  => project,
+                          :user     => anon,
+                          :activity => activity)
+    assert_equal 1, te.errors.count
+
+    te = TimeEntry.create(:spent_on => '2010-01-01',
+                          :hours    => 25,
+                          :issue    => issue,
+                          :project  => project,
+                          :user     => anon,
+                          :activity => activity)
+    assert_equal 1, te.errors.count
   end
 
   def test_acitivity_should_belong_to_project_activities