diff --git a/icalendar.ts b/icalendar.ts
index 3f3560f..f54a2c9 100644
--- a/icalendar.ts
+++ b/icalendar.ts
@@ -30,15 +30,25 @@ const RRULE_KEY_MAP: Record<string, string> = {
 };
 
 /**
- * Formats an RRULE value for the string representation.
- * Specifically handles Date objects and nested date objects from ts-ics.
+ * Robustly formats an RRULE value for its string representation.
+ * Handles:
+ * - Arrays: joins elements with commas (recursive)
+ * - Date objects: formats as YYYYMMDDTHHMMSSZ
+ * - Objects: extracts .date, .day, or .value properties (recursive)
+ * - Primitives: stringifies directly
  */
 function formatRRuleValue(v: any): string {
+  if (Array.isArray(v)) {
+    return v.map((item) => formatRRuleValue(item)).join(",");
+  }
   if (v instanceof Date) {
     return v.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z";
   }
-  if (typeof v === "object" && v !== null && v.date instanceof Date) {
-    return v.date.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z";
+  if (typeof v === "object" && v !== null) {
+    const val = v.date || v.day || v.value;
+    if (val !== undefined) {
+      return formatRRuleValue(val);
+    }
   }
   return String(v);
 }
diff --git a/icalendar_test.ts b/icalendar_test.ts
index 5707e11..cec9c10 100644
--- a/icalendar_test.ts
+++ b/icalendar_test.ts
@@ -226,7 +226,7 @@ Deno.test("expandRecurrences - object rrule with until", () => {
 });
 
 
-Deno.test("expandRecurrences - object rrule with byday (Reproduction)", () => {
+Deno.test("expandRecurrences - object rrule with byday", () => {
   const now = new Date();
   const start = new Date(now.getTime() - 10 * 86400000); 
   const startStr = localDateString(start);
@@ -237,22 +237,9 @@ Deno.test("expandRecurrences - object rrule with byday (Reproduction)", () => {
     rrule: { frequency: "WEEKLY", byday: [{ day: "MO" }, { day: "WE" }] } 
   };
   
-  // Spy on console.error
-  let errorLogged = false;
-  const originalConsoleError = console.error;
-  console.error = (...args) => {
-    if (args[0].includes("Error expanding recurrence for Object RRULE BYDAY Event") && 
-        args[1].message.includes("Invalid weekday string: [object Object]")) {
-      errorLogged = true;
-    }
-  };
-
-  try {
-    expandRecurrences(icsEvent, 30);
-  } finally {
-    console.error = originalConsoleError;
-  }
-
-  assert(errorLogged, "Should have logged an error for invalid BYDAY object values");
+  const results = expandRecurrences(icsEvent, 30);
+  // Should now return multiple occurrences
+  assert(results.length > 1, `Expected > 1 occurrences, got ${results.length}`);
+  assertEquals(results[0].recurrent, true);
 });