example.rb

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

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

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

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

class User < Dry::Types::Struct
  CreepyRailsDate = Types::Date.constructor { |value| .. }
  
  attribute :name, Types::String
  attribute :birth_date, CreepyRailsDate
end