the spatial rotation of a vector quantity is describable by the curl. It is defined as the vector or outer or cross product of the differential vector operator

, called del or nabla with any arbitrary vector. In 3D Cartesian notations, it is given by
the nabla operator is a space vector rate of change differential operator in contradistinction to the time scalar rate of change differential operator.
What is the equivalent temporal rotation of a vector quantity? Can there exist a curl operator with respect to time? In almost all wave phenomena, this time rate of change operator seems to be functionally associated to the concept of frequency for all periodic functons. Therefore the subtlety lies between the physical concept of rotation and the concept of vibration or oscillation.