I don't know of any requirement that specific. In one of my previous posts I believe I described how in some circumstances you may not have to have a label.
The bottom line is that you must have a method that ensures the measurements made by any instrument are properly traceable to some standard units of measure (that is a VERY abbreviated description of a lot of detail requirements).
It is not quite so important how the label is worded. What is more important is that the user/operator of the calibrated instrument knows when he or she can or cannot use that instrument to make measurements.
I have heard in some instances having a chart on a wall listing due dates for instruments (operators had to be trained to assure they knew how to understand the chart). I have heard of using color coded dots (same rules). I began developing a label-less method where all measuring instruments were on a production database with due dates entered, so that a past due instrument could not be used in the system. There are a lot of variations on what could be used.
All that rambling to say that no, it does not matter whether CAL or CALIBRATION, or DUE or DATE DUE. What is important is knowing that users absolutely know how to, and demonstrate that they know how to interpret them, and that instruments absolutely will not be used past the due date.
I might recommend that which ever wording you use, be sure it is defined in your policy, so your labeling is unambiguous.