text: Title: Problem with cron expressions
  Body: Hi,
  
  Very odd. The cron expression engine does not accept `0 2 * * *`... It accepts `0 1 * * *` and `0 3 * * *`.
  
  ![image](https://user-images.githubusercontent.com/1027111/47313789-1f871e80-d640-11e8-9b4c-4cb36e524494.png)
  
  ![image](https://user-images.githubusercontent.com/1027111/47313802-2746c300-d640-11e8-9dda-ca75e8cfcb7c.png)
  
  ![image](https://user-images.githubusercontent.com/1027111/47313827-3fb6dd80-d640-11e8-9500-03647f997f70.png)
  