-- data that will be useful for active-buffer:

|weekday: _list> => |day: monday> + |day: tuesday> + |day: wednesday> + |day: thursday> + |day: friday>
|weekend: _list> => |day: saturday> + |day: sunday>

|day: monday> => |weekday: _list> + |weekday>
|day: tuesday> => |weekday: _list> + |weekday>
|day: wednesday> => |weekday: _list> + |weekday>
|day: thursday> => |weekday: _list> + |weekday>
|day: friday> => |weekday: _list> + |weekday>
|day: saturday> => |weekend: _list> + |weekend>
|day: sunday> => |weekend: _list> + |weekend>