Question: I can't understand why the server returns the 404 status error code if the wrong route is registered.
The server should return 400 status error code.
I would like to know what this may be related to.

[postman](https://i.stack.imgur.com/7wVSK.png)

Answer: 
Make [`DatePicker`](https://medium.com/flutter-community/a-deep-dive-into-datepicker-in-flutter-37e84f7d8d6c) instead of keyboard to ensure a proper format.
You should really use a DatePicker: [What is the correct way to add date picker in flutter app?](https://stackoverflow.com/questions/52727535/what-is-the-correct-way-to-add-date-picker-in-flutter-app)

If you insist on doing it the non-standard way, you can use a FilteringTextInputFormatter: [Flutter - Regex in TextFormField](https://stackoverflow.com/questions/56390839/flutter-regex-in-textformfield)