Type '"DateValue | undefined"' is not assignable to type '"'DateValue' is unresolvable "'.ts(2322)

Hello, i am an absolute beginner when it comes to ArkType and i am trying adapt my project while following allowing the https://arktype.io/docs/intro/your-first-type intro. When trying to adopt the example to my real life type, i am getting the error mentioned in the title. DateValue itself is a union type of some classes. What i am doing wrong?