Fix problems with times in timezone offsets which are not multiples of an hour.

Truncate does something we do not expect in the case of non integer
hour timezone offset. Its basically rounding to hour from t = 0. Which
in this case is Unix t=0 ... which means it rounds to the half hour.

spec.go

@@ -108,7 +108,7 @@ WRAP:
 	for 1<<uint(t.Hour())&s.Hour == 0 {
 		if !added {
 			added = true
-			t = t.Truncate(time.Hour)
+			t = time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), 0, 0, 0, t.Location())
 		}
 		t = t.Add(1 * time.Hour)
 

spec_test.go

@@ -202,3 +202,48 @@ func getTime(value string) time.Time {
 
 	return t
 }
+
+func TestNextWithTz(t *testing.T) {
+	runs := []struct {
+		time, spec string
+		expected   string
+	}{
+		// Failing tests
+		{"2016-01-03T13:09:03+0530", "0 14 14 * * *", "2016-01-03T14:14:00+0530"},
+		{"2016-01-03T04:09:03+0530", "0 14 14 * * ?", "2016-01-03T14:14:00+0530"},
+
+		// Passing tests
+		{"2016-01-03T14:09:03+0530", "0 14 14 * * *", "2016-01-03T14:14:00+0530"},
+		{"2016-01-03T14:00:00+0530", "0 14 14 * * ?", "2016-01-03T14:14:00+0530"},
+	}
+	for _, c := range runs {
+		sched, err := Parse(c.spec)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		actual := sched.Next(getTimeTZ(c.time))
+		expected := getTimeTZ(c.expected)
+		if !actual.Equal(expected) {
+			t.Errorf("%s, \"%s\": (expected) %v != %v (actual)", c.time, c.spec, expected, actual)
+		}
+	}
+}
+
+func getTimeTZ(value string) time.Time {
+	if value == "" {
+		return time.Time{}
+	}
+	t, err := time.Parse("Mon Jan 2 15:04 2006", value)
+	if err != nil {
+		t, err = time.Parse("Mon Jan 2 15:04:05 2006", value)
+		if err != nil {
+			t, err = time.Parse("2006-01-02T15:04:05-0700", value)
+			if err != nil {
+				panic(err)
+			}
+		}
+	}
+
+	return t
+}