Cron Extension
Cron allows users to schedule pipeline runs on long term intervals and specific days.
It uses a stripped down version of the cron syntax to do so:
Field           Allowed values  Allowed special characters
Minutes         0-59            * , -
Hours           0-23            * , -
Day of month    1-31            * , -
Month           1-12            * , -
Day of week     0-6             * , -
Year            1970-2100       * , -
┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of the month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday)
│ │ │ │ │ ┌───────────── Year (1970-2100)
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ │ │
* * * * * *
Pipeline Configuration
- expression- : Specifies the cron expression of the interval desired. 
Every year on Xmas
gofer pipeline extend simple cron yearly_on_xmas -s expression="0 1 25 12 * *"
Extension Configuration
None