If you are listed as Full-Time or Part-Time in Zenefits, you can enroll in commuter benefits at any time. The only regulation is that you must enroll into the plan by the 25th of the month for your plan to be effective the first of the very next month.
Employers must set up the plan on the 15th of the month to be effective the first of the next month, and employees would then have a minimum of ten days to enroll in the plan. If the employee misses the initial enrollment they will still be able to enroll the following month. Employees may enroll or cancel the plan whenever they would like.