To write the Events element (Ev) in the index.

§1. There are two tables, one for timed events, the other for those of no fixed time. 

void EventsElement::render(OUTPUT_STREAM, index_session *session) {
    localisation_dictionary *LD = Indexing::get_localisation(session);
    tree_inventory *inv = Indexing::get_inventory(session);
    InterNodeList::array_sort(inv->rule_nodes, MakeSynopticModuleStage::module_order);

    int when_count = 0, tt_count = 0;
    Index events with no specific time1.1;
    Index timetabled events1.2;
    if ((when_count == 0) && (tt_count == 0)) {
        HTML_OPEN("p");
        Localisation::italic(OUT, LD, I"Index.Elements.Ev.None");
        HTML_CLOSE("p");
    }
}

§1.1. Index events with no specific time1.1 = 

    inter_package *pack;
    LOOP_OVER_INVENTORY_PACKAGES(pack, i, inv->rule_nodes)
        if ((Metadata::exists(pack, I"^timed")) &&
            (Metadata::exists(pack, I"^timed_for") == FALSE)) {
            if (when_count == 0) {
                HTML_OPEN("p");
                Localisation::italic(OUT, LD, I"Index.Elements.Ev.Timeless");
                HTML_CLOSE("p");
            }
            when_count++;
            HTML_OPEN_WITH("p", "class=\"tightin2\"");
            WRITE("%S", Metadata::required_textual(pack, I"^preamble"));
            IndexUtilities::link_package(OUT, pack);
            WRITE(" (");
            Localisation::roman(OUT, LD, I"Index.Elements.Ev.WhereTriggered");
            WRITE(": ");
            inter_package *entry;
            LOOP_THROUGH_SUBPACKAGES(entry, pack, I"_timed_rule_trigger") {
                int at = (int) Metadata::read_optional_numeric(entry, I"^used_at");
                if (at > 0) IndexUtilities::link(OUT, at);
            }
            WRITE(")");
            HTML_CLOSE("p");
        }

§1.2. Index timetabled events1.2 = 

    inter_package *pack;
    LOOP_OVER_INVENTORY_PACKAGES(pack, i, inv->rule_nodes)
        if ((Metadata::exists(pack, I"^timed")) &&
            (Metadata::exists(pack, I"^timed_for"))) {
            if (tt_count == 0) {
                HTML_OPEN("p");
                Localisation::italic(OUT, LD, I"Index.Elements.Ev.Timetable");
                HTML_CLOSE("p");
            }
            tt_count++;
            HTML_OPEN_WITH("p", "class=\"in2\"");
            WRITE("%S", Metadata::required_textual(pack, I"^preamble"));
            IndexUtilities::link_package(OUT, pack);
            HTML_CLOSE("p");
        }