I'd recommend starting the challenge on or around Samhain (usually 31st October in the Northern Hemisphere). You can complete the course at a pace that suits you. If you miss a day, just start afresh the following day.

You can view the study material on a mobile device but using a desktop or laptop will enhance your experience and enjoyment of the course. 

Disclaimer

Before you begin any new exercise program, it is recommended that you seek medical advice from your healthcare provider. You have full responsibility for your safety and should know your limits. Before practicing asana poses as described on this course, be sure that you are well informed of proper practice and do not take risks beyond your experience and comfort levels. The author recommends common sense when contemplating the practices described on this course and assumes no liability for any injuries caused to course participants that may result from their use of the content contained herein.