As long as you complete a course by its expiration date, it can be claimed for credit within your biennium. The course is credited to the date it is completed, not the date that it is submitted.
The ARRT requires that all certificates display the expiration date of the activity completed. For live lecture, the expiration date may be the date of the lecture. For self-learning activities, the expiration date may be several months in the future. Expiration dates are usually one, two or three years from the evaluation date of the course. The expiration date of self-learning activities can be extended after re-evaluation of the material's content and relevancy. The expiration date ensures that technologists are completing appropriate courses with current and relevant content.