The search for the next execution time can be limited by a date/time barrier so searches for february 30th will no longer result in an endless loop

src/main/java/fc/cron/CronExpression.java

@@ -174,6 +174,20 @@ public class CronExpression {
     }
 
     public DateTime nextTimeAfter(DateTime afterTime) {
+        // will search for the next time within the next 4 years. If there is no
+        // time matching, an InvalidArgumentException will be thrown (it is very
+        // likely that the cron expression is invalid, like the February 30th).
+        return nextTimeAfter(afterTime, afterTime.plusYears(4));
+    }
+
+    public DateTime nextTimeAfter(DateTime afterTime, long durationInMillis) {
+        // will search for the next time within the next durationInMillis
+        // millisecond. Be aware that the duration is specified in millis,
+        // but in fact the limit is checked on a day-to-day basis.
+        return nextTimeAfter(afterTime, afterTime.plus(durationInMillis));
+    }
+
+    public DateTime nextTimeAfter(DateTime afterTime, DateTime dateTimeBarrier) {
         MutableDateTime nextTime = new MutableDateTime(afterTime);
         nextTime.setMillisOfSecond(0);
         nextTime.secondOfDay().add(1);
@@ -207,6 +221,7 @@ public class CronExpression {
                     }
                     nextTime.addDays(1);
                     nextTime.setTime(0, 0, 0, 0);
+                    checkIfDateTimeBarrierIsReached(nextTime, dateTimeBarrier);
                 }
                 if (monthField.matches(nextTime.getMonthOfYear())) {
                     break;
@@ -214,17 +229,25 @@ public class CronExpression {
                 nextTime.addMonths(1);
                 nextTime.setDayOfMonth(1);
                 nextTime.setTime(0, 0, 0, 0);
+                checkIfDateTimeBarrierIsReached(nextTime, dateTimeBarrier);
             }
             if (dayOfWeekField.matches(new LocalDate(nextTime))) {
                 break;
             }
             nextTime.addDays(1);
             nextTime.setTime(0, 0, 0, 0);
+            checkIfDateTimeBarrierIsReached(nextTime, dateTimeBarrier);
         }
 
         return nextTime.toDateTime();
     }
 
+    private static void checkIfDateTimeBarrierIsReached(MutableDateTime nextTime, DateTime dateTimeBarrier) {
+        if (nextTime.isAfter(dateTimeBarrier)) {
+            throw new IllegalArgumentException("No next execution time could be determined that is before the limit of " + dateTimeBarrier);
+        }
+    }
+
     @Override
     public String toString() {
         return getClass().getSimpleName() + "<" + expr + ">";

src/test/java/fc/cron/CronExpressionTest.java

@@ -442,4 +442,28 @@ public class CronExpressionTest {
     public void shall_not_not_support_rolling_period() throws Exception {
         new CronExpression("* * 5-1 * * *");
     }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void non_existing_date_throws_exception() throws Exception {
+        // Will check for the next 4 years - no 30th of February is found so a IAE is thrown.
+        new CronExpression("* * * 30 2 *").nextTimeAfter(DateTime.now());
+    }
+
+    @Test
+    public void test_default_barrier() throws Exception {
+        // the default barrier is 4 years - so leap years are considered.
+        assertThat(new CronExpression("* * * 29 2 *").nextTimeAfter(new DateTime(2012, 3, 1, 00, 00))).isEqualTo(new DateTime(2016, 2, 29, 00, 00));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void test_one_year_barrier() throws Exception {
+        // The next leap year is 2016, so an IllegalArgumentException is expected.
+        new CronExpression("* * * 29 2 *").nextTimeAfter(new DateTime(2012, 3, 1, 00, 00), new DateTime(2013, 3, 1, 00, 00));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void test_two_year_barrier() throws Exception {
+        // The next leap year is 2016, so an IllegalArgumentException is expected.
+        new CronExpression("* * * 29 2 *").nextTimeAfter(new DateTime(2012, 3, 1, 00, 00), 1000 * 60 * 60 * 24 * 356 * 2);
+    }
 }