Definition of revolutions per minute unit: = Hz/60. The number of cycles that occurred in one minute. Cycle may be periodically repeating event. Symbol is rpm (revolutions per minute), it is the sixtieth part of Hertz.
Definition of revolutions per day unit: = Hz/86400. The number of events or cycles that occurred in one day. The sign rpd (revolutions per day) the value if Hertz / 86400. It is used to express slow frequencies. The Earth's rotational frequency is 1 rpd (revolution per day)