Threshold / Due date picker doesn't roll over to the next month when incremented

[fatuhoku]

Reproduction:

1. Open SwiftToDo Desktop app.
2. Create any task.
3. Select it, press 't' to open Threshold date dialog.
4. Set the value to the last day of the month, e.g. 31/03/2023 ensuring 31 (day) is selected
5. Click the 'up ' ˄ caret to increment.
6. Observe that the date value is now 01/03/2023

Optional: 7. Cry.