diff --git a/app/controllers/assessment/handin.rb b/app/controllers/assessment/handin.rb
index d7888696..22b9839e 100755
--- a/app/controllers/assessment/handin.rb
+++ b/app/controllers/assessment/handin.rb
@@ -270,6 +270,13 @@ def log_submit
       render(plain: err, status: :bad_request) && return
     end
 
+    # Validate assessment dates
+    current_time = Time.current
+    if current_time < @assessment.start_at || current_time > @assessment.end_at
+      err = "ERROR: Submissions are not allowed outside the assessment period"
+      render(plain: err, status: :bad_request) && return
+    end
+
     @result = params[:result]
     render(plain: "ERROR: No result!", status: :bad_request) && return unless @result
 
diff --git a/spec/controllers/assessments_controller_spec.rb b/spec/controllers/assessments_controller_spec.rb
index 7f2b4ce0..addef635 100644
--- a/spec/controllers/assessments_controller_spec.rb
+++ b/spec/controllers/assessments_controller_spec.rb
@@ -212,4 +212,113 @@
       end
     end
   end
+
+  describe "log_submit" do
+    context "when the date is inside of the assessment period" do
+      let!(:course_hash) { create_course_with_users_as_hash }
+      let!(:valid_assessment) do
+        assessment_path = Rails.root.join("courses/#{course_hash[:course].name}/assessment_valid")
+        FileUtils.mkdir_p(assessment_path)
+        FileUtils.mkdir_p("#{assessment_path}/handin")
+        assessment = FactoryBot.create(
+          :assessment,
+          name: "assessment_valid",
+          course: course_hash[:course],
+          start_at: 2.days.ago,
+          due_at: 1.day.from_now,
+          end_at: 2.days.from_now,
+          allow_unofficial: true
+        )
+        assessment.save!
+        assessment
+      end
+
+      it "allows a valid log submission" do
+        user = course_hash[:students_cud].first
+        params = {
+          course_name: course_hash[:course].name,
+          name: valid_assessment.name,
+          user: user.email,
+          result: "test result"
+        }
+        post(:log_submit, params:)
+        expect(response).to have_http_status(:ok)
+        expect(response.body).to eq("OK")
+      end
+    end
+
+    context "when the submission is before the start date" do
+      let!(:course_hash) { create_course_with_users_as_hash }
+      let!(:invalid_assessment) do
+        assessment_path = Rails.root.join(
+          "courses/#{course_hash[:course].name}/assessment_invalid_date"
+        )
+        FileUtils.mkdir_p(assessment_path)
+        FileUtils.mkdir_p("#{assessment_path}/handin")
+        assessment = FactoryBot.create(
+          :assessment,
+          name: "assessment_invalid_date",
+          course: course_hash[:course],
+          start_at: 1.day.from_now,
+          due_at: 2.days.from_now,
+          end_at: 3.days.from_now,
+          allow_unofficial: true
+        )
+        assessment.save!
+        assessment
+      end
+
+      it "rejects a log submission for having invalid dates" do
+        user = course_hash[:students_cud].first
+        params = {
+          course_name: course_hash[:course].name,
+          name: invalid_assessment.name,
+          user: user.email,
+          result: "test result"
+        }
+        post(:log_submit, params:)
+        expect(response).to have_http_status(:bad_request)
+        expect(response.body).to eq(
+          "ERROR: Submissions are not allowed outside the assessment period"
+        )
+      end
+    end
+
+    context "when the submission is after the end date" do
+      let!(:course_hash) { create_course_with_users_as_hash }
+      let!(:expired_assessment) do
+        assessment_path = Rails.root.join(
+          "courses/#{course_hash[:course].name}/assessment_expired"
+        )
+        FileUtils.mkdir_p(assessment_path)
+        FileUtils.mkdir_p("#{assessment_path}/handin")
+        assessment = FactoryBot.create(
+          :assessment,
+          name: "assessment_expired",
+          course: course_hash[:course],
+          start_at: 3.days.ago,
+          due_at: 2.days.ago,
+          end_at: 1.day.ago,
+          allow_unofficial: true
+        )
+        assessment.save!
+        assessment
+      end
+
+      it "rejects a log submission for having invalid dates" do
+        user = course_hash[:students_cud].first
+        params = {
+          course_name: course_hash[:course].name,
+          name: expired_assessment.name,
+          user: user.email,
+          result: "test result"
+        }
+        post(:log_submit, params:)
+        expect(response).to have_http_status(:bad_request)
+        expect(response.body).to eq(
+          "ERROR: Submissions are not allowed outside the assessment period"
+        )
+      end
+    end
+  end
 end