How to add date fields in the scope rules (property restrictions)

Hi,

I am trying to add property restrictions on date field of a rule in
scopes in the central administration (in the search settings).
Modified=[Today] and created = 4/4/2008 throws error and there are no
results for this query. But if I use Author=admin in the property
restriction, it works. How can I set property restrictions on date
fields? I basically need to use [Today] in the properties restriction
query.

Thanks.