diff --git a/astrbot/core/astr_main_agent.py b/astrbot/core/astr_main_agent.py
index ee007140b..cee6e9e27 100644
--- a/astrbot/core/astr_main_agent.py
+++ b/astrbot/core/astr_main_agent.py
@@ -115,6 +115,15 @@ from astrbot.core.utils.quoted_message_parser import (
 from astrbot.core.utils.string_utils import normalize_and_dedupe_strings
 
 LLM_ERROR_MESSAGE_EXTRA_KEY = "_llm_error_message"
+WEEKDAY_NAMES = (
+    "Monday",
+    "Tuesday",
+    "Wednesday",
+    "Thursday",
+    "Friday",
+    "Saturday",
+    "Sunday",
+)
 WEB_SEARCH_CITATION_TOOL_NAMES = frozenset(
     {
         "web_search_baidu",
@@ -874,18 +883,17 @@ def _append_system_reminders(
                 system_parts.append(f"Group name: {group_name}")
 
     if cfg.get("datetime_system_prompt"):
-        current_time = None
+        now = None
         if timezone:
             try:
                 now = datetime.datetime.now(zoneinfo.ZoneInfo(timezone))
-                current_time = now.strftime("%Y-%m-%d %H:%M (%Z)")
             except Exception as exc:  # noqa: BLE001
                 logger.error("时区设置错误: %s, 使用本地时区", exc)
-        if not current_time:
-            current_time = (
-                datetime.datetime.now().astimezone().strftime("%Y-%m-%d %H:%M (%Z)")
-            )
-        system_parts.append(f"Current datetime: {current_time}")
+        if now is None:
+            now = datetime.datetime.now().astimezone()
+        current_time = now.strftime("%Y-%m-%d %H:%M (%Z)")
+        weekday = WEEKDAY_NAMES[now.weekday()]
+        system_parts.append(f"Current datetime: {current_time}, Weekday: {weekday}")
 
     if system_parts:
         system_content = (
diff --git a/tests/unit/test_astr_main_agent.py b/tests/unit/test_astr_main_agent.py
index 84f354894..31c80e09e 100644
--- a/tests/unit/test_astr_main_agent.py
+++ b/tests/unit/test_astr_main_agent.py
@@ -1,5 +1,6 @@
 """Tests for astr_main_agent module."""
 
+import datetime
 import os
 from unittest.mock import AsyncMock, MagicMock, patch
 
@@ -134,6 +135,39 @@ def _setup_conversation_for_build(conv_mgr, cid: str = "conv-id") -> MagicMock:
     return conversation
 
 
+def test_append_system_reminders_includes_weekday(mock_event):
+    """Test datetime reminder includes weekday information."""
+    req = ProviderRequest(prompt="Hello")
+    fixed_now = datetime.datetime(
+        2026,
+        6,
+        8,
+        12,
+        34,
+        tzinfo=datetime.timezone.utc,
+    )
+
+    class FixedDateTime(datetime.datetime):
+        @classmethod
+        def now(cls, tz=None):
+            if tz:
+                return fixed_now.astimezone(tz)
+            return fixed_now
+
+    with patch("astrbot.core.astr_main_agent.datetime.datetime", FixedDateTime):
+        ama._append_system_reminders(
+            mock_event,
+            req,
+            {"datetime_system_prompt": True},
+            "UTC",
+        )
+
+    assert [part.text for part in req.extra_user_content_parts] == [
+        "<system_reminder>Current datetime: "
+        "2026-06-08 12:34 (UTC), Weekday: Monday</system_reminder>"
+    ]
+
+
 class TestMainAgentBuildConfig:
     """Tests for MainAgentBuildConfig dataclass."""