package MyApp::Controller::WhatEver;
use warnings;
use strict;
use parent "Catalyst::Controller";
use Date::Calc "check_date";

sub by_date : Path("d") Args(3) {
    my ( $self, $c, $yyyy, $mm, $dd ) = @_;
    $c->detach( YOUR_404_HANDLER ) unless eval { check_date($yyyy,$mm,$dd) };
    my $some_rs = $c->model("Your::Schema")->search({ ...use dates... });
    $some_rs->count || $c->detach( YOUR_404_HANDLER );
}