What does "RF Cal" means?

I'm using Samsung Galaxy S5. When I entered in the dial *#12580*369#, it appeared some information about the phone. One of them is "RF Cal" (it is formatted like a date). 1. Does anyone knows what it is? 2. What does "RF Cal" stands for? 3. Where did this terminology come from? What organization/person coined it? 4. If "RF Cal" is the manufacturing date of the phone, then why not just call it the manufacturing date of MFD for example? Is it because there is a difference?