Calculated Fields problem (iOS)

I am writing regarding problems with calculated fields in TapForms for iOS. I had written previously about this, and you had made changes I requested, but the behavior has reverted in recent versions, and is probably even a bit flakier than it once was.

To illustrate, I have a form where I record typical daily events in the care of my (originally infant) now toddler daughter. It’s meant to be a quick way to record things as they happen so I can later know how much she’s slept, when she last pooped (sorry!) and so forth.

For some of these events (the sleep events), I want to know the durations. For everything else, I don’t care.

So, long story short, I have two date/time fields: [Event start] and [Event end]. And I have a calculated field, [Duration], which is [Event end] – [Event start]. For every kind of event, I record the [Event start]. For the sleep events, I also record [Event end].

I expect that records with no value in [Event end] should show nothing in [Duration], but instead they show things like “-392947 hrs, 39 mins”.

In the record list view, I include the [Duration] field, but if a given record has no duration value (or should have no value), I would expect [Duration] to be omitted from the display. That’s how other types of fields are handled in the list view, but all the records show their [Duration] values.

Finally, the actual calculations don’t always work upon first entering the value in [Event end]. Sometimes I have to go back and re-save [Event start] for the calculation to execute.

I’m attaching screenshots, so hopefully all of this will be clear.