1:- module(bc_headers, [
    2    bc_if_modified_since/2 % +Request, -Time
    3]).

 bc_if_modified_since(+Request, -Time) is semidet

Extracts and parses If-Modified-Since header from the request. Fails when the request contains no such header.

   11bc_if_modified_since(Request, Time):-
   12    memberchk(if_modified_since(Text), Request),
   13    parse_time(Text, rfc_1123, Time)