It would be really useful to be able to filter the child record's based on a DateTime field's value. For example a roll up field on account to calculate the sum of the value of orders placed in the current month.
Agreed. The current limitations of roll up fields filtrering criterias on date fields are greatly limiting the potentials. Having the ability to do as the author suggests or have a roll up fields based on a rolling window would open op a host of new options.
