--- In firebird-support@yahoogroups.com, "Ivan
Prenosil" <Ivan.Prenosil@...> wrote:

> You can use it directly
>
> SELECT
> EXTRACT(DAY FROM (MyDate - EXTRACT(DAY FROM MyDate) + 32
> - EXTRACT(DAY FROM MyDate - EXTRACT(DAY FROM MyDate) + 32)))
> FROM MyTable;
>
> or store that expression into computed column.
>

Thank you Ivan, that is I want to do!