example.rb

class User < Dry::Types::Struct
  attribute :name, Types::String
  attribute :birth_day, Types::Date
end

UserSchema = Dry::Validation.Schema do
  key(:name).required
  key(:birth_date).required(:date?)
end

User.new(
  UserSchema.with(input_processor: :json)
            .call(name: "Joe", birth_date: "2012-04-23T18:25:43.511Z")
            .output
)