Artist tours have start and end dates. When an artist makes more than one tour, their list of tours should be sorted by date rather than by alphabetical order, like all other relationships with dates are.

For example, currently neither https://musicbrainz.org/series/39f153ed-afb4-403c-8ee2-f942973e9bc8 nor its https://musicbrainz.org/relationship/f03d59f3-97db-424b-885e-e8be69d65225 relationship are able to store or load start and end dates.