This depends on the course you choose. Students enrolled in The Fundamentals of Montessori Education workshops can be completed in 2 days as it is an introductory course.
If you are looking to complete a Diploma of Montessori Early Childhood Education at a Montessori institute, you will have 1 to 2 years to receive to complete the Diploma qualification requirements after you have completed your application form to study Montessori Education.