last daily observation in a month (not lbusdate)

is there a way to keep only the last observation in a month from a datenum vector? For example

A=

        729530
        729537
        729544
        729551
        729558
        729565

That is

20-May-1997
27-May-1997
03-Jun-1997
10-Jun-1997
17-Jun-1997
24-Jun-1997

So the new vector should be only rows 2 and 6.

B=
729537
729565

This is not lbusdate.

Answer 1

[Dave]

Solved, used accumarray with @max