In our example, we want to return only very recent items, problems reported in the last five days.
We use a Fetch Feed module to grab the Atom feed (http://www.us-cert.gov/current/index.atom), and pipe it into a Filter module. We "permit items that match all of the following", and add a rule for the item.y:published.utime field. We'll filter if this value is greater than some value.
But what value? What we want is a utime value corresponding to five days ago. We can't just type "5 days ago" into the value field for the Filter rule -- that won't work. Instead, we add a Date Builder module and enter "5 days ago" into its Date field. Then we wire Date Builder into the Filter module's value field.
Because Date Builder outputs a datetime value, the Filter field recognizes it as such and converts to a drop-down list box. From this list we can select any of the datetime fields, including utime.
Now our feed only outputs items from the last five days.
Pipe Web Address: http://pipes.yahoo.com/pipes_team/ugTTcuNS3BG36ht98ivLAg