diff --git a/spec/perfect_sched_spec.rb b/spec/perfect_sched_spec.rb
index 3a6811e..165215e 100644
--- a/spec/perfect_sched_spec.rb
+++ b/spec/perfect_sched_spec.rb
@@ -1,7 +1,7 @@
 require 'spec_helper'
 
 describe PerfectSched do
-  context '.open' do
+  describe '.open' do
     let (:config){ double('config') }
     let (:client){ double('client') }
     let (:schedule_collection){ double('schedule_collection') }
@@ -24,40 +24,83 @@
     end
   end
 
-  context 'cron_time' do
+  describe '.cron_time' do
     it do
-      ts = PerfectSched.cron_time('0 * * * *', 0, nil)
-      expect(ts).not_to be_nil
+      ts = PerfectSched.cron_time('0 * * * *', 1, nil)
+      expect(ts).to eq 3600
     end
     it do
       expect{PerfectSched.cron_time('0 * * * *', 0, 'JST-9')}.to raise_error(ArgumentError)
     end
+    it do
+      ts = PerfectSched.cron_time('0,30 * * * *', 1, nil)
+      expect(ts).to eq 1800
+    end
+    it do
+      ts = PerfectSched.cron_time('*/7 * * * *', 1, nil)
+      expect(ts).to eq 420
+    end
+    it do
+      ts = PerfectSched.cron_time('0-59/7 * * * *', 421, nil)
+      expect(ts).to eq 840
+    end
+    it 'supports @hourly' do
+      ts = PerfectSched.cron_time('@hourly', 1, nil)
+      expect(ts).to eq 3600
+    end
+    it 'supports @daily' do
+      ts = PerfectSched.cron_time('@daily', 1, nil)
+      expect(ts).to eq 86400
+    end
+    it 'supports @monthly' do
+      ts = PerfectSched.cron_time('@monthly', 1, nil)
+      expect(ts).to eq 2678400
+    end
   end
 
-  context '.next_time' do
-    it do
-      ts = PerfectSched.next_time('0 * * * *', 0, nil)
-      expect(ts).not_to be_nil
+  describe '.next_time' do
+    it 'can run hourly cron' do
+      ts = PerfectSched.next_time(' 0 * * * * ', 0, nil)
+      expect(ts).to eq 3600
     end
-    xit 'calculates 4 years quickly' do
+    it 'calculates 4 years quickly' do
       t = Time.utc(2012,2,29)
       ts = PerfectSched.next_time('0 0 29 2 *', t.to_i, nil)
       expect(ts).to eq(Time.utc(2016,2,29).to_i)
     end
-    it do
+    it 'raises error on unsupported timezone' do
       expect{PerfectSched.next_time('0 * * * *', 0, 'JST-9')}.to raise_error(ArgumentError)
     end
-
+    it 'returns next run time of given time' do
+      t0 = Time.new(2015, 12,  3,  1,  0,  0,  9*3600)
+      t1 = Time.new(2015, 12,  3,  2,  0,  0,  9*3600)
+      ts = PerfectSched.next_time('0 * * * *', t0.to_i, 'Asia/Tokyo')
+      expect(ts).to eq(t1.to_i)
+    end
+    it 'returns next run time of given time' do
+      t0 = Time.new(2015, 12,  3,  1, 59, 59,  9*3600)
+      t1 = Time.new(2015, 12,  3,  2,  0,  0,  9*3600)
+      ts = PerfectSched.next_time('0 * * * *', t0.to_i, 'Asia/Tokyo')
+      expect(ts).to eq(t1.to_i)
+    end
+    it 'returns next run time with day of week (0=Sun)' do
+      t0 = Time.new(2015, 12,  3,  0,  0,  0,  9*3600)
+      t1 = Time.new(2015, 12,  6,  0,  0,  0,  9*3600)
+      ts = PerfectSched.next_time('0 0 * * 0', t0.to_i, 'Asia/Tokyo')
+      expect(ts).to eq(t1.to_i)
+    end
     context 'DST 2015' do
-      it 'can go through America/Los_Angeles transition' do
-        t0 = Time.new(2015,  3,  8,  1, 59, 59, -8*3600)
-        t1 = Time.new(2015,  3,  9,  2,  0,  0, -7*3600) # 2015-03-08T02:00:00 doesn't exist
-        ts = PerfectSched.next_time('* 2 * * *', t0.to_i, 'America/Los_Angeles')
+      it 'skips task on 8 Mar because 1:59:59 PST -> 3:00:00 PDT' do
+        t0 = Time.new(2015,  3,  7,  2,  0,  0, -8*3600)
+        # 2015-03-08T02:00:00 doesn't exist
+        t1 = Time.new(2015,  3,  9,  2,  0,  0, -7*3600)
+        ts = PerfectSched.next_time('0 2 * * *', t0.to_i, 'America/Los_Angeles')
         expect(ts).to eq(t1.to_i)
       end
-      it 'can go through America/Los_Angeles transition' do
+      it 'runs twice on Nov 11 because 1:59:59 PDT -> 1:00:00 PST' do
+        # 2015-11-01T01:00:00 exists twice
         t0 = Time.new(2015, 11,  1,  1,  0,  0, -7*3600)
-        t1 = Time.new(2015, 11,  1,  1,  0,  0, -8*3600) # 2015-11-01T01:00:00 exists twice
+        t1 = Time.new(2015, 11,  1,  1,  0,  0, -8*3600)
         ts = PerfectSched.next_time('0 1 * * *', t0.to_i, 'America/Los_Angeles')
         expect(ts).to eq(t1.to_i)
       end