If the user enters an invalid string such as "25:00" into the start time field or the end/due time field, IncidenceDateTime does not detect it, because the QDateTime constructor used by currentStartDateTime() and currentEndDateTime() treats it as "00:00".
- detects and reports the error,
- uses more specific error messages,
- focuses on the erroneous field, and
- logs at "debug" level, because the problem isn't very big.