[HELP] Spring Boot: field is not set in request

I'm learning Spring Boot. My learning project is in this repository github.

I have this controller where in the method createTodo I have as RequestBody this dto where I have the problem that only the field "when" is not filled properly when I make a post on that controller route.
I tried to insert a log but I didn't succeed. I don't know why all the other field are filled and only "when" not.
This is an example of the body to the call at such route:

{
"what": "Buy bread",
"when": "2022-06-01 19:00:00",
"where": "To the grocery store"
}