29 CFR § 785.27 - General.

Attendance at lectures, meetings, training programs and similar activities need not be counted as working time if the following four criteria are met:

(a) Attendance is outside of the employee's regular working hours;

(b) Attendance is in fact voluntary;

(c) The course, lecture, or meeting is not directly related to the employee's job; and

(d) The employee does not perform any productive work during such attendance.