Creating or editing Crontabs is never easy. A single incorrect value can destroy the entire schedule task. So to prevent such disasters it is always advisable to cross verify the configuration against multiple resources. The below is a list of URLs that you can rely on.
- https://crontab.guru/ – simple to use and more stable
- http://corntab.com/ – another simple free service
- https://crontab-generator.org/ – with some advanced features
- http://www.cronmaker.com/ – my personal preference with advanced features
