Is there anytime during the semester when an undergrad may not request admission to the major or minor?

No, there are no time restrictions related to discussing a change of major or minor or entering the degree program. If you wish to discuss admission to the undergraduate major or one of the undergraduate minors, you may contact the Undergraduate Coordinator, Dr. Martha Whitaker, by email at marthaw@email.arizona.edu or by telephone (520-621-9715) at any time during the semester.