When can we expect our appraisal letter and from which month our revise salary will be credited?

I guess it’s effective from 1st of April , Band release by first week of April followed letter release by 15th April is what I heard, This is the first time am coming across this process as well

You will get a band first in the month of April and then you will get an appraisal letter and the revised salary will be credited in the month of may