m0useanswered grow question a month ago Agree with Papa_T, it only says it been updated when you add in a new week to it. Editing existing weeks does nothing in terms of its "update age" despite it being updated.
In theory you could populate and entire dairy germinationvegflowerharvest with null data and placeholders then fill it in as you go and it would still be as old as the last week created from day one. However after a few hours you can not edit parts of the harvest as it locks in reviews and some other stuff from what I have seen.