date_time_input in Core Catalog looks and behaves poorly #543
Description
The core catalog's combined date and time picker flow exhibits inconsistent behavior regarding its output value, often losing either the date or the time component based on where the user dismisses the flow. Additionally, the default output formatting is overly complex and should be simplified and made configurable.
Reproduction Steps
- Open the date/time picker component in the core catalog gallery app (where both date and time selection are enabled).
- Complete the Date Picker step.
- Immediately dismiss the flow (e.g., by hitting "Cancel" or clicking outside the modal) after selecting the date but before interacting with or completing the Time Picker.
Observed Result: The field value is set to only the time (often the current or default time), and the selected date is lost/not reflected in the output value.