This required some big overhauls. The view model no longer takes records. It only takes the date that it is responsible for, and it will ask the database for records pertaining to that date. This means that once the view model has saved all of its records, it can simply reload those records from the database. This has the effect that as soon as the user moves from DayEdit back to DayDetail, all of the interesting information has been repopulated.
I've created the DaySummary structure and set up a list view to go into
the historical view. One hard-coded date is visible as a placeholder to
start filling things into the day summary.