Changing Taxonomy Names – Events Manager

Hi, is it possible to change the name of the taxonomies?

For example I want to change ‘Category’ to ‘Activity’

I tried

function revcon_change_cat_label() {
    global $submenu;
    $submenu['edit.php'][15][0] = 'Authors'; // Rename categories to Authors
}
add_action( 'admin_menu', 'revcon_change_cat_label' );

and

function revcon_change_cat_object() {
????global $wp_taxonomies;
????$labels = &$wp_taxonomies['category']->labels;
????$labels->name = 'Author';
????$labels->singular_name = 'Author';
????$labels->add_new = 'Add Author';
????$labels->add_new_item = 'Add Author';
????$labels->edit_item = 'Edit Author';
????$labels->new_item = 'Author';
????$labels->view_item = 'View Author';
????$labels->search_items = 'Search Authors';
????$labels->not_found = 'No Authors found';
????$labels->not_found_in_trash = 'No Authors found in Trash';
????$labels->all_items = 'All Authors';
????$labels->menu_name = 'Author';
????$labels->name_admin_bar = 'Author';
}
add_action( 'init', 'revcon_change_cat_object' );

But this changes the main theme taxonomies.