How to use timestamp in spec rpm? -

can use current timestamp ( or day, or else uniq param ) release in spec rpm file ?

for example, this:

release: 100%{?dist}.test.%{timestamp} 

what can define variable before preamble, use on release line. following example set release number (assuming september 12, 2013) 20130912.

%define build_timestamp %(date +"%y%m%d")  ... release: %{build_timestamp}