Querying by the node's own dates

CreatedUtc and ChangedUtc are indexed for every node of every type. Query them through NodeMeta, whether or not the type maps them to members:

// recently changed articles
db.Query<IArticle>().OrderByMetaDescending(m => m.ChangedUtc).Page(0, 50).Execute();
db.Query<IArticle>().WhereMeta(m => m.CreatedUtc >= since).Count();

A [CreatedUtcProperty] or [ChangedUtcProperty] member answers the same queries from the same index: OrderByDescending(x => x.ChangedUtc). In a query string the two are n._createdUtc and n._changedUtc. No other NodeMeta field can be queried.