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, localisation_dictionary *LD) {
    inter_tree *I = InterpretIndex::get_tree();
    tree_inventory *inv = Synoptic::inv(I);
    TreeLists::sort(inv->rule_nodes, Synoptic::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"); WRITE("<i>None.</i>"); HTML_CLOSE("p");
    }
}

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

    for (int i=0; i<TreeLists::len(inv->rule_nodes); i++) {
        inter_package *pack = Inter::Package::defined_by_frame(inv->rule_nodes->list[i].node);
        if (Metadata::exists(pack, I"^timed")) {
            if (Metadata::exists(pack, I"^timed_for") == FALSE) {
                if (when_count == 0) {
                    HTML_OPEN("p");
                    WRITE("<i>Events with no specific time</i>");
                    HTML_CLOSE("p");
                }
                when_count++;
                HTML_OPEN_WITH("p", "class=\"tightin2\"");
                WRITE("%S", Metadata::read_textual(pack, I"^preamble"));
                int at = (int) Metadata::read_optional_numeric(pack, I"^at");
                if (at > 0) IndexUtilities::link(OUT, at);
                WRITE(" (where triggered: ");
                inter_tree_node *D = Inter::Packages::definition(pack);
                LOOP_THROUGH_INTER_CHILDREN(C, D) {
                    if (C->W.data[ID_IFLD] == PACKAGE_IST) {
                        inter_package *entry = Inter::Package::defined_by_frame(C);
                        if (Inter::Packages::type(entry) == PackageTypes::get(I, 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 = 

    for (int i=0; i<TreeLists::len(inv->rule_nodes); i++) {
        inter_package *pack = Inter::Package::defined_by_frame(inv->rule_nodes->list[i].node);
        if (Metadata::exists(pack, I"^timed")) {
            if (Metadata::exists(pack, I"^timed_for")) {
                if (tt_count == 0) {
                    HTML_OPEN("p");
                    WRITE("<i>Timetable</i>");
                    HTML_CLOSE("p");
                }
                tt_count++;
                HTML_OPEN_WITH("p", "class=\"in2\"");
                WRITE("%S", Metadata::read_textual(pack, I"^preamble"));
                int at = (int) Metadata::read_optional_numeric(pack, I"^at");
                if (at > 0) IndexUtilities::link(OUT, at);
                HTML_CLOSE("p");
            }
        }
    }