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.
DayDetailViewModel needs testing. I've worked out an improved API, and a set of tests to go along with it, and those can be made more easily with a mockable RecordProvider. So, in addition to stubbing out a bunch of tests, I've also created RecordProvider, mocked it, and implemented it for App.