✅ Phase 3 complete: DateTimeBox fully implemented and tested

Co-authored-by: moe-charm <217100418+moe-charm@users.noreply.github.com>

test_datetime_box.nyash

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+// test_datetime_box.nyash - DateTimeBox functionality test
+// Phase 3: DateTimeBox implementation validation
+
+print("📅 Testing DateTimeBox implementation...")
+
+// Basic DateTimeBox creation
+local now, timestamp_dt, parsed_dt, result
+
+// Test 1: Current time creation
+now = new DateTimeBox()
+print("Current time: " + now.toString())
+
+// Test 2: Timestamp creation  
+timestamp_dt = new DateTimeBox(1640995200)  // 2022-01-01 00:00:00 UTC
+print("From timestamp: " + timestamp_dt.toString())
+
+// Test 3: Date component extraction
+result = now.year()
+print("Current year: " + result.toString())
+
+result = now.month()
+print("Current month: " + result.toString())
+
+result = now.day()
+print("Current day: " + result.toString())
+
+result = now.hour()
+print("Current hour: " + result.toString())
+
+result = now.minute()
+print("Current minute: " + result.toString())
+
+result = now.second()
+print("Current second: " + result.toString())
+
+// Test 4: Date arithmetic
+result = now.addDays(7)
+print("7 days from now: " + result.toString())
+
+result = now.addHours(24)
+print("24 hours from now: " + result.toString())
+
+print("✅ DateTimeBox Phase 3 tests completed!")