Have to disagree with you there,whoop-whoop.........
The CAA's PLD (Personnel Licensing Dep't)have
(surprise,surprise)!,actually made things as simple as possible.
They have recently amended the rules governing validity periods,and brought LPC's into line with OPC's.
Now,no matter why you are conducting an LPC,
(initial,renewal,or revalidation)the validity period will now always run to the end of the month.
Therefore,the "Aircraft Rating valid until date"that you enter into a pilots licence,should now ALWAYS be the last day of the month.