From a6cffea588670333e27a58617712a05d7aa6f556 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <kou@clear-code.com>
Date: Mon, 26 Jan 2026 23:52:56 +0900
Subject: [PATCH] GH-48990: [Ruby] Add support for writing date arrays

---
 .../red-arrow-format/lib/arrow-format/type.rb | 21 ++++++++-
 ruby/red-arrow-format/test/test-reader.rb     |  6 +--
 ruby/red-arrow-format/test/test-writer.rb     | 46 +++++++++++++++++++
 3 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/ruby/red-arrow-format/lib/arrow-format/type.rb b/ruby/red-arrow-format/lib/arrow-format/type.rb
index c648e5b63137..b3b5bf7aba9b 100644
--- a/ruby/red-arrow-format/lib/arrow-format/type.rb
+++ b/ruby/red-arrow-format/lib/arrow-format/type.rb
@@ -330,10 +330,21 @@ def build_array(size, validity_buffer, values_buffer)
     end
   end
 
-  class TemporalType < Type
+  class TemporalType < PrimitiveType
   end
 
   class DateType < TemporalType
+    attr_reader :unit
+    def initialize(unit)
+      super()
+      @unit = unit
+    end
+
+    def to_flatbuffers
+      fb_type = FB::Date::Data.new
+      fb_type.unit = FB::DateUnit.try_convert(@unit.to_s.upcase)
+      fb_type
+    end
   end
 
   class Date32Type < DateType
@@ -343,6 +354,10 @@ def singleton
       end
     end
 
+    def initialize
+      super(:day)
+    end
+
     def name
       "Date32"
     end
@@ -359,6 +374,10 @@ def singleton
       end
     end
 
+    def initialize
+      super(:millisecond)
+    end
+
     def name
       "Date64"
     end
diff --git a/ruby/red-arrow-format/test/test-reader.rb b/ruby/red-arrow-format/test/test-reader.rb
index e00489673760..d59ae9cb1685 100644
--- a/ruby/red-arrow-format/test/test-reader.rb
+++ b/ruby/red-arrow-format/test/test-reader.rb
@@ -191,7 +191,7 @@ def test_read
         sub_test_case("Date64") do
           def setup(&block)
             @date_2017_08_28_00_00_00 = 1503878400000
-            @date_2025_12_09_00_00_00 = 1765324800000
+            @date_2025_12_10_00_00_00 = 1765324800000
             super(&block)
           end
 
@@ -199,7 +199,7 @@ def build_array
             Arrow::Date64Array.new([
                                      @date_2017_08_28_00_00_00,
                                      nil,
-                                     @date_2025_12_09_00_00_00,
+                                     @date_2025_12_10_00_00_00,
                                    ])
           end
 
@@ -209,7 +209,7 @@ def test_read
                              "value" => [
                                @date_2017_08_28_00_00_00,
                                nil,
-                               @date_2025_12_09_00_00_00,
+                               @date_2025_12_10_00_00_00,
                              ],
                            },
                          ],
diff --git a/ruby/red-arrow-format/test/test-writer.rb b/ruby/red-arrow-format/test/test-writer.rb
index 24a49b3777f3..31c2bef299ae 100644
--- a/ruby/red-arrow-format/test/test-writer.rb
+++ b/ruby/red-arrow-format/test/test-writer.rb
@@ -42,6 +42,10 @@ def convert_type(red_arrow_type)
       ArrowFormat::Float32Type.singleton
     when Arrow::DoubleDataType
       ArrowFormat::Float64Type.singleton
+    when Arrow::Date32DataType
+      ArrowFormat::Date32Type.singleton
+    when Arrow::Date64DataType
+      ArrowFormat::Date64Type.singleton
     when Arrow::BinaryDataType
       ArrowFormat::BinaryType.singleton
     when Arrow::LargeBinaryDataType
@@ -220,6 +224,48 @@ def test_write
           end
         end
 
+        sub_test_case("Date32") do
+          def setup(&block)
+            @date_2017_08_28 = 17406
+            @date_2025_12_09 = 20431
+            super(&block)
+          end
+
+          def build_array
+            Arrow::Date32Array.new([@date_2017_08_28, nil, @date_2025_12_09])
+          end
+
+          def test_write
+            assert_equal([Date.new(2017, 8, 28), nil, Date.new(2025, 12, 9)],
+                         @values)
+          end
+        end
+
+        sub_test_case("Date64") do
+          def setup(&block)
+            @date_2017_08_28_00_00_00 = 1503878400000
+            @date_2025_12_10_00_00_00 = 1765324800000
+            super(&block)
+          end
+
+          def build_array
+            Arrow::Date64Array.new([
+                                     @date_2017_08_28_00_00_00,
+                                     nil,
+                                     @date_2025_12_10_00_00_00,
+                                   ])
+          end
+
+          def test_write
+            assert_equal([
+                           DateTime.new(2017, 8, 28, 0, 0, 0),
+                           nil,
+                           DateTime.new(2025, 12, 10, 0, 0, 0),
+                         ],
+                         @values)
+          end
+        end
+
         sub_test_case("Binary") do
           def build_array
             Arrow::BinaryArray.new(["Hello".b, nil, "World".b])